{"group":{"id":1,"name":"Community","lockable":false,"created_at":"2012-01-18T18:02:15.000Z","updated_at":"2026-05-26T00:16:20.000Z","description":"Problems submitted by members of the MATLAB Central community.","is_default":true,"created_by":161519,"badge_id":null,"featured":false,"trending":false,"solution_count_in_trending_period":0,"trending_last_calculated":"2026-05-26T00:00:00.000Z","image_id":null,"published":true,"community_created":false,"status_id":2,"is_default_group_for_player":false,"deleted_by":null,"deleted_at":null,"restored_by":null,"restored_at":null,"description_opc":null,"description_html":null,"published_at":null},"problems":[{"id":2836,"title":"Modify subscripts - easier","description":"MATLAB supports object-oriented programming. Let's take an advantage of it in cody.\r\n\r\nThis problem focus on modifying subscripted references for class double.\r\n\r\nThis example shows classical behavior: \r\n\r\n  \u003e\u003e A = [1 4 7\r\n          2 5 8\r\n          3 6 9];\r\n  \u003e\u003e A([1 3], [3 1])\r\n\r\n  ans =\r\n\r\n     7     1\r\n     9     3\r\n\r\nWhile this is what I am looking for:\r\n\r\n  \u003e\u003e modified_A = sub_double(A);\r\n  \u003e\u003e modified_A([1 3], [3 1])\r\n  \r\n  ans = \r\n  \r\n     7     3\r\n\r\n  \u003e\u003e modified_A([1 2 2], [3 1 2])\r\n  \r\n  ans = \r\n  \r\n     7     2     5\r\n\r\nIf there are given two subscripts vectors of the same lenght, return only those values which correspond to paired subscriptions.\r\n\r\n*Task*: You are given class template. Complete it to achieve desired behaviour.\r\n\r\nAdditional info:\r\n\r\n\r\n* If you are not familiar with classes in MATLAB you can find more information \u003chttp://www.mathworks.com/help/matlab/matlab_oop/class-definition.html here\u003e and \u003chttp://www.mathworks.com/help/matlab/customize-matlab-behavior.html here\u003e or you can find it typing:\r\n\r\n    \u003e\u003e doc 'Class Definition'\r\n    \u003e\u003e doc 'Customize MATLAB Behavior'\r\n    \r\n    \r\n* Feel free to modify the template,\r\n* You can try your skills to write a function instead of a class. You can use anonymus functions, etc.,\r\n* Using classes open another doors to cheat (easily).  This is not a hacking problem, so please respect it (you can create some new, interesting problems :-) ),\r\n* In this form it is solvable without using function \"builtin\" which is forbidden in cody. I can allow it in the testsuite if there will be need for it,\r\n* Look for more problems using tags below\r\n\r\nEnjoy!","description_html":"\u003cp\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/p\u003e\u003cp\u003eThis problem focus on modifying subscripted references for class double.\u003c/p\u003e\u003cp\u003eThis example shows classical behavior:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A = [1 4 7\r\n        2 5 8\r\n        3 6 9];\r\n\u0026gt;\u0026gt; A([1 3], [3 1])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans =\r\n\u003c/pre\u003e\u003cpre\u003e     7     1\r\n     9     3\u003c/pre\u003e\u003cp\u003eWhile this is what I am looking for:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; modified_A = sub_double(A);\r\n\u0026gt;\u0026gt; modified_A([1 3], [3 1])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e     7     3\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; modified_A([1 2 2], [3 1 2])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e     7     2     5\u003c/pre\u003e\u003cp\u003eIf there are given two subscripts vectors of the same lenght, return only those values which correspond to paired subscriptions.\u003c/p\u003e\u003cp\u003e\u003cb\u003eTask\u003c/b\u003e: You are given class template. Complete it to achieve desired behaviour.\u003c/p\u003e\u003cp\u003eAdditional info:\u003c/p\u003e\u003cul\u003e\u003cli\u003eIf you are not familiar with classes in MATLAB you can find more information \u003ca href = \"http://www.mathworks.com/help/matlab/matlab_oop/class-definition.html\"\u003ehere\u003c/a\u003e and \u003ca href = \"http://www.mathworks.com/help/matlab/customize-matlab-behavior.html\"\u003ehere\u003c/a\u003e or you can find it typing:\u003c/li\u003e\u003c/ul\u003e\u003cpre\u003e    \u0026gt;\u0026gt; doc 'Class Definition'\r\n    \u0026gt;\u0026gt; doc 'Customize MATLAB Behavior'\u003c/pre\u003e\u003cul\u003e\u003cli\u003eFeel free to modify the template,\u003c/li\u003e\u003cli\u003eYou can try your skills to write a function instead of a class. You can use anonymus functions, etc.,\u003c/li\u003e\u003cli\u003eUsing classes open another doors to cheat (easily).  This is not a hacking problem, so please respect it (you can create some new, interesting problems :-) ),\u003c/li\u003e\u003cli\u003eIn this form it is solvable without using function \"builtin\" which is forbidden in cody. I can allow it in the testsuite if there will be need for it,\u003c/li\u003e\u003cli\u003eLook for more problems using tags below\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eEnjoy!\u003c/p\u003e","function_template":"classdef sub_double \u003c double\r\n  methods\r\n    function obj = sub_double(in)\r\n      obj = obj@double(in);\r\n    end\r\n    function out = subsref(obj,S)\r\n        % ???? \r\n    end\r\n  end \r\nend","test_suite":"%%\r\n% first some basic tests\r\nA = 1;\r\nB = sub_double(A);\r\ny = B(1);\r\ny_correct = 1;\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 1]);\r\ny_correct = [3 7];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 end]);\r\ny_correct = [3 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(1,[3 1]);\r\ny_correct = [3 1];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(2:end);\r\ny_correct = [4 7 2 5 8 3 6 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(5);\r\nB = sub_double(A);\r\ny = B([1 5 4 3 2],[3 4 5 1 2]);\r\ny_correct = [1:5];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(7);\r\nB = sub_double(A);\r\nrows = randi(7,1,10);\r\ncols = randi(7,1,10);\r\ny = B(rows,cols);\r\ny_correct = arrayfun(@(R,C)A(R,C),rows,cols);\r\nassert(isequal(y,y_correct))\r\n","published":true,"deleted":false,"likes_count":3,"comments_count":4,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":14,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-01-18T00:16:14.000Z","updated_at":"2026-05-28T04:22:04.000Z","published_at":"2015-01-18T00:23:22.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis problem focus on modifying subscripted references for class double.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis example shows classical behavior:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[\u003e\u003e A = [1 4 7\\n        2 5 8\\n        3 6 9];\\n\u003e\u003e A([1 3], [3 1])\\n\\nans =\\n\\n     7     1\\n     9     3]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eWhile this is what I am looking for:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[\u003e\u003e modified_A = sub_double(A);\\n\u003e\u003e modified_A([1 3], [3 1])\\n\\nans = \\n\\n     7     3\\n\\n\u003e\u003e modified_A([1 2 2], [3 1 2])\\n\\nans = \\n\\n     7     2     5]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIf there are given two subscripts vectors of the same lenght, return only those values which correspond to paired subscriptions.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eTask\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e: You are given class template. Complete it to achieve desired behaviour.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eAdditional info:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIf you are not familiar with classes in MATLAB you can find more information\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/help/matlab/matlab_oop/class-definition.html\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehere\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e and\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/help/matlab/customize-matlab-behavior.html\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehere\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e or you can find it typing:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[    \u003e\u003e doc 'Class Definition'\\n    \u003e\u003e doc 'Customize MATLAB Behavior']]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFeel free to modify the template,\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eYou can try your skills to write a function instead of a class. You can use anonymus functions, etc.,\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eUsing classes open another doors to cheat (easily). This is not a hacking problem, so please respect it (you can create some new, interesting problems :-) ),\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIn this form it is solvable without using function \\\"builtin\\\" which is forbidden in cody. I can allow it in the testsuite if there will be need for it,\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLook for more problems using tags below\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eEnjoy!\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":2837,"title":"Modify subscripts","description":"MATLAB supports object-oriented programming. Let's take an advantage of it in cody.\r\n\r\nThis problem starts \u003chttp://uk.mathworks.com/matlabcentral/cody/problems/2836-class-ics-modify-subscripts-easy here\u003e.\r\n\r\nLet's take things a bit more seriously. There are _subsasgn_ and _subsref_ to overload:\r\n\r\n  \u003e\u003e A = sub_double([ 1 4 7\r\n                      2 5 8\r\n                      3 6 9]);\r\n  \u003e\u003e A([1 3],[3 1])\r\n  \r\n  ans = \r\n\r\n    3x3 sub_double:\r\n\r\n    double data:    \r\n       7    3\r\n  \r\n  \u003e\u003e A([1 2 3],[3 2 1]) = 0\r\n  \r\n  A = \r\n\r\n    3x3 sub_double:\r\n\r\n    double data:\r\n       1     2     0\r\n       4     0     6\r\n       0     8     9\r\n\r\n  \u003e\u003e A(:)'\r\n  \r\n  ans = \r\n  \r\n    1x9 sub_double:\r\n  \r\n    double data:\r\n       1     4     0     2     0     8     0     6     9\r\n  \r\n  \u003e\u003e A(:,:)\r\n  \r\n  ans = \r\n  \r\n    1x3 sub_double:\r\n  \r\n    double data:\r\n       1     0     9\r\n\r\n\r\n","description_html":"\u003cp\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/p\u003e\u003cp\u003eThis problem starts \u003ca href = \"http://uk.mathworks.com/matlabcentral/cody/problems/2836-class-ics-modify-subscripts-easy\"\u003ehere\u003c/a\u003e.\u003c/p\u003e\u003cp\u003eLet's take things a bit more seriously. There are \u003ci\u003esubsasgn\u003c/i\u003e and \u003ci\u003esubsref\u003c/i\u003e to overload:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A = sub_double([ 1 4 7\r\n                    2 5 8\r\n                    3 6 9]);\r\n\u0026gt;\u0026gt; A([1 3],[3 1])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e    3x3 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:    \r\n       7    3\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A([1 2 3],[3 2 1]) = 0\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eA = \r\n\u003c/pre\u003e\u003cpre\u003e    3x3 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:\r\n       1     2     0\r\n       4     0     6\r\n       0     8     9\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A(:)'\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e    1x9 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:\r\n       1     4     0     2     0     8     0     6     9\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A(:,:)\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e    1x3 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:\r\n       1     0     9\u003c/pre\u003e","function_template":"classdef sub_double \u003c double\r\n  methods\r\n    function obj = sub_double(in)\r\n      obj = obj@double(in);\r\n    end\r\n    function out = subsref(obj,S)\r\n        \r\n    end\r\n  end \r\nend","test_suite":"%%\r\n% first some basic tests\r\nA = 1;\r\nB = sub_double(A);\r\ny = B(1);\r\ny_correct = 1;\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 1]);\r\ny_correct = [3 7];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 end]);\r\ny_correct = [3 9];\r\nassert(isequal(y,double(y_correct)))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(1,[3 1]);\r\ny_correct = [3 1];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(2:end);\r\ny_correct = [4 7 2 5 8 3 6 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(5);\r\nB = sub_double(A);\r\ny = B([1 5 4 3 2],[3 4 5 1 2]);\r\ny_correct = [1:5];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(7);\r\nB = sub_double(A);\r\nrows = randi(7,1,10);\r\ncols = randi(7,1,10);\r\ny = B(rows,cols);\r\ny_correct = arrayfun(@(R,C)A(R,C),rows,cols);\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = 1;\r\nB = sub_double(A);\r\nB(1) = 3;\r\nA = 3;\r\nassert(isequal(A,B))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\nB([1 2 3],[3 2 1]) = 0;\r\nA = [1 2 0\r\n     4 0 6\r\n     0 8 9];\r\nassert(isequal(A,B))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\nB([1 3],[3 end]) = [7 7];\r\nA = [1 2 7\r\n     4 5 6\r\n     7 8 7];\r\nassert(isequal(double(A),double(B)))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(:,:);\r\ny_correct = [1 5 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\nB(2:end) = [2:9];\r\nA = A';\r\nassert(isequal(B,A))\r\n%%\r\nA = magic(5);\r\nB = sub_double(A);\r\nB([1 5 4 3 2],[3 4 5 1 2])=0;\r\nassert(isequal(sum(~[B B']),ones(1,10)))\r\n%%\r\nA = magic(7);\r\nB = sub_double(A);\r\nrows = randi(7,1,10);\r\ncols = randi(7,1,10);\r\nvals = randi(7,1,10);\r\nB(rows,cols) = vals;\r\nfor k = 1:10\r\n  A(rows(k),cols(k))=vals(k);\r\nend\r\nassert(isequal(A,B))","published":true,"deleted":false,"likes_count":1,"comments_count":0,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":10,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-01-18T00:53:33.000Z","updated_at":"2026-05-28T04:22:20.000Z","published_at":"2015-01-18T01:36:53.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis problem starts\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://uk.mathworks.com/matlabcentral/cody/problems/2836-class-ics-modify-subscripts-easy\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehere\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLet's take things a bit more seriously. There are\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:i/\u003e\u003c/w:rPr\u003e\u003cw:t\u003esubsasgn\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e and\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:i/\u003e\u003c/w:rPr\u003e\u003cw:t\u003esubsref\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e to overload:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[\u003e\u003e A = sub_double([ 1 4 7\\n                    2 5 8\\n                    3 6 9]);\\n\u003e\u003e A([1 3],[3 1])\\n\\nans = \\n\\n    3x3 sub_double:\\n\\n    double data:    \\n       7    3\\n\\n\u003e\u003e A([1 2 3],[3 2 1]) = 0\\n\\nA = \\n\\n    3x3 sub_double:\\n\\n    double data:\\n       1     2     0\\n       4     0     6\\n       0     8     9\\n\\n\u003e\u003e A(:)'\\n\\nans = \\n\\n    1x9 sub_double:\\n\\n    double data:\\n       1     4     0     2     0     8     0     6     9\\n\\n\u003e\u003e A(:,:)\\n\\nans = \\n\\n    1x3 sub_double:\\n\\n    double data:\\n       1     0     9]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"problem_search":{"problems":[{"id":2836,"title":"Modify subscripts - easier","description":"MATLAB supports object-oriented programming. Let's take an advantage of it in cody.\r\n\r\nThis problem focus on modifying subscripted references for class double.\r\n\r\nThis example shows classical behavior: \r\n\r\n  \u003e\u003e A = [1 4 7\r\n          2 5 8\r\n          3 6 9];\r\n  \u003e\u003e A([1 3], [3 1])\r\n\r\n  ans =\r\n\r\n     7     1\r\n     9     3\r\n\r\nWhile this is what I am looking for:\r\n\r\n  \u003e\u003e modified_A = sub_double(A);\r\n  \u003e\u003e modified_A([1 3], [3 1])\r\n  \r\n  ans = \r\n  \r\n     7     3\r\n\r\n  \u003e\u003e modified_A([1 2 2], [3 1 2])\r\n  \r\n  ans = \r\n  \r\n     7     2     5\r\n\r\nIf there are given two subscripts vectors of the same lenght, return only those values which correspond to paired subscriptions.\r\n\r\n*Task*: You are given class template. Complete it to achieve desired behaviour.\r\n\r\nAdditional info:\r\n\r\n\r\n* If you are not familiar with classes in MATLAB you can find more information \u003chttp://www.mathworks.com/help/matlab/matlab_oop/class-definition.html here\u003e and \u003chttp://www.mathworks.com/help/matlab/customize-matlab-behavior.html here\u003e or you can find it typing:\r\n\r\n    \u003e\u003e doc 'Class Definition'\r\n    \u003e\u003e doc 'Customize MATLAB Behavior'\r\n    \r\n    \r\n* Feel free to modify the template,\r\n* You can try your skills to write a function instead of a class. You can use anonymus functions, etc.,\r\n* Using classes open another doors to cheat (easily).  This is not a hacking problem, so please respect it (you can create some new, interesting problems :-) ),\r\n* In this form it is solvable without using function \"builtin\" which is forbidden in cody. I can allow it in the testsuite if there will be need for it,\r\n* Look for more problems using tags below\r\n\r\nEnjoy!","description_html":"\u003cp\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/p\u003e\u003cp\u003eThis problem focus on modifying subscripted references for class double.\u003c/p\u003e\u003cp\u003eThis example shows classical behavior:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A = [1 4 7\r\n        2 5 8\r\n        3 6 9];\r\n\u0026gt;\u0026gt; A([1 3], [3 1])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans =\r\n\u003c/pre\u003e\u003cpre\u003e     7     1\r\n     9     3\u003c/pre\u003e\u003cp\u003eWhile this is what I am looking for:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; modified_A = sub_double(A);\r\n\u0026gt;\u0026gt; modified_A([1 3], [3 1])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e     7     3\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; modified_A([1 2 2], [3 1 2])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e     7     2     5\u003c/pre\u003e\u003cp\u003eIf there are given two subscripts vectors of the same lenght, return only those values which correspond to paired subscriptions.\u003c/p\u003e\u003cp\u003e\u003cb\u003eTask\u003c/b\u003e: You are given class template. Complete it to achieve desired behaviour.\u003c/p\u003e\u003cp\u003eAdditional info:\u003c/p\u003e\u003cul\u003e\u003cli\u003eIf you are not familiar with classes in MATLAB you can find more information \u003ca href = \"http://www.mathworks.com/help/matlab/matlab_oop/class-definition.html\"\u003ehere\u003c/a\u003e and \u003ca href = \"http://www.mathworks.com/help/matlab/customize-matlab-behavior.html\"\u003ehere\u003c/a\u003e or you can find it typing:\u003c/li\u003e\u003c/ul\u003e\u003cpre\u003e    \u0026gt;\u0026gt; doc 'Class Definition'\r\n    \u0026gt;\u0026gt; doc 'Customize MATLAB Behavior'\u003c/pre\u003e\u003cul\u003e\u003cli\u003eFeel free to modify the template,\u003c/li\u003e\u003cli\u003eYou can try your skills to write a function instead of a class. You can use anonymus functions, etc.,\u003c/li\u003e\u003cli\u003eUsing classes open another doors to cheat (easily).  This is not a hacking problem, so please respect it (you can create some new, interesting problems :-) ),\u003c/li\u003e\u003cli\u003eIn this form it is solvable without using function \"builtin\" which is forbidden in cody. I can allow it in the testsuite if there will be need for it,\u003c/li\u003e\u003cli\u003eLook for more problems using tags below\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eEnjoy!\u003c/p\u003e","function_template":"classdef sub_double \u003c double\r\n  methods\r\n    function obj = sub_double(in)\r\n      obj = obj@double(in);\r\n    end\r\n    function out = subsref(obj,S)\r\n        % ???? \r\n    end\r\n  end \r\nend","test_suite":"%%\r\n% first some basic tests\r\nA = 1;\r\nB = sub_double(A);\r\ny = B(1);\r\ny_correct = 1;\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 1]);\r\ny_correct = [3 7];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 end]);\r\ny_correct = [3 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(1,[3 1]);\r\ny_correct = [3 1];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(2:end);\r\ny_correct = [4 7 2 5 8 3 6 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(5);\r\nB = sub_double(A);\r\ny = B([1 5 4 3 2],[3 4 5 1 2]);\r\ny_correct = [1:5];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(7);\r\nB = sub_double(A);\r\nrows = randi(7,1,10);\r\ncols = randi(7,1,10);\r\ny = B(rows,cols);\r\ny_correct = arrayfun(@(R,C)A(R,C),rows,cols);\r\nassert(isequal(y,y_correct))\r\n","published":true,"deleted":false,"likes_count":3,"comments_count":4,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":14,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-01-18T00:16:14.000Z","updated_at":"2026-05-28T04:22:04.000Z","published_at":"2015-01-18T00:23:22.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis problem focus on modifying subscripted references for class double.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis example shows classical behavior:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[\u003e\u003e A = [1 4 7\\n        2 5 8\\n        3 6 9];\\n\u003e\u003e A([1 3], [3 1])\\n\\nans =\\n\\n     7     1\\n     9     3]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eWhile this is what I am looking for:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[\u003e\u003e modified_A = sub_double(A);\\n\u003e\u003e modified_A([1 3], [3 1])\\n\\nans = \\n\\n     7     3\\n\\n\u003e\u003e modified_A([1 2 2], [3 1 2])\\n\\nans = \\n\\n     7     2     5]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIf there are given two subscripts vectors of the same lenght, return only those values which correspond to paired subscriptions.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:b/\u003e\u003c/w:rPr\u003e\u003cw:t\u003eTask\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e: You are given class template. Complete it to achieve desired behaviour.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eAdditional info:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIf you are not familiar with classes in MATLAB you can find more information\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/help/matlab/matlab_oop/class-definition.html\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehere\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e and\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://www.mathworks.com/help/matlab/customize-matlab-behavior.html\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehere\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e or you can find it typing:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[    \u003e\u003e doc 'Class Definition'\\n    \u003e\u003e doc 'Customize MATLAB Behavior']]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eFeel free to modify the template,\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eYou can try your skills to write a function instead of a class. You can use anonymus functions, etc.,\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eUsing classes open another doors to cheat (easily). This is not a hacking problem, so please respect it (you can create some new, interesting problems :-) ),\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eIn this form it is solvable without using function \\\"builtin\\\" which is forbidden in cody. I can allow it in the testsuite if there will be need for it,\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"ListParagraph\\\"/\u003e\u003cw:numPr\u003e\u003cw:numId w:val=\\\"1\\\"/\u003e\u003c/w:numPr\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLook for more problems using tags below\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eEnjoy!\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"},{"id":2837,"title":"Modify subscripts","description":"MATLAB supports object-oriented programming. Let's take an advantage of it in cody.\r\n\r\nThis problem starts \u003chttp://uk.mathworks.com/matlabcentral/cody/problems/2836-class-ics-modify-subscripts-easy here\u003e.\r\n\r\nLet's take things a bit more seriously. There are _subsasgn_ and _subsref_ to overload:\r\n\r\n  \u003e\u003e A = sub_double([ 1 4 7\r\n                      2 5 8\r\n                      3 6 9]);\r\n  \u003e\u003e A([1 3],[3 1])\r\n  \r\n  ans = \r\n\r\n    3x3 sub_double:\r\n\r\n    double data:    \r\n       7    3\r\n  \r\n  \u003e\u003e A([1 2 3],[3 2 1]) = 0\r\n  \r\n  A = \r\n\r\n    3x3 sub_double:\r\n\r\n    double data:\r\n       1     2     0\r\n       4     0     6\r\n       0     8     9\r\n\r\n  \u003e\u003e A(:)'\r\n  \r\n  ans = \r\n  \r\n    1x9 sub_double:\r\n  \r\n    double data:\r\n       1     4     0     2     0     8     0     6     9\r\n  \r\n  \u003e\u003e A(:,:)\r\n  \r\n  ans = \r\n  \r\n    1x3 sub_double:\r\n  \r\n    double data:\r\n       1     0     9\r\n\r\n\r\n","description_html":"\u003cp\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/p\u003e\u003cp\u003eThis problem starts \u003ca href = \"http://uk.mathworks.com/matlabcentral/cody/problems/2836-class-ics-modify-subscripts-easy\"\u003ehere\u003c/a\u003e.\u003c/p\u003e\u003cp\u003eLet's take things a bit more seriously. There are \u003ci\u003esubsasgn\u003c/i\u003e and \u003ci\u003esubsref\u003c/i\u003e to overload:\u003c/p\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A = sub_double([ 1 4 7\r\n                    2 5 8\r\n                    3 6 9]);\r\n\u0026gt;\u0026gt; A([1 3],[3 1])\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e    3x3 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:    \r\n       7    3\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A([1 2 3],[3 2 1]) = 0\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eA = \r\n\u003c/pre\u003e\u003cpre\u003e    3x3 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:\r\n       1     2     0\r\n       4     0     6\r\n       0     8     9\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A(:)'\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e    1x9 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:\r\n       1     4     0     2     0     8     0     6     9\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003e\u0026gt;\u0026gt; A(:,:)\r\n\u003c/pre\u003e\u003cpre class=\"language-matlab\"\u003eans = \r\n\u003c/pre\u003e\u003cpre\u003e    1x3 sub_double:\u003c/pre\u003e\u003cpre\u003e    double data:\r\n       1     0     9\u003c/pre\u003e","function_template":"classdef sub_double \u003c double\r\n  methods\r\n    function obj = sub_double(in)\r\n      obj = obj@double(in);\r\n    end\r\n    function out = subsref(obj,S)\r\n        \r\n    end\r\n  end \r\nend","test_suite":"%%\r\n% first some basic tests\r\nA = 1;\r\nB = sub_double(A);\r\ny = B(1);\r\ny_correct = 1;\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 1]);\r\ny_correct = [3 7];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B([1 3],[3 end]);\r\ny_correct = [3 9];\r\nassert(isequal(y,double(y_correct)))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(1,[3 1]);\r\ny_correct = [3 1];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(2:end);\r\ny_correct = [4 7 2 5 8 3 6 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(5);\r\nB = sub_double(A);\r\ny = B([1 5 4 3 2],[3 4 5 1 2]);\r\ny_correct = [1:5];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = magic(7);\r\nB = sub_double(A);\r\nrows = randi(7,1,10);\r\ncols = randi(7,1,10);\r\ny = B(rows,cols);\r\ny_correct = arrayfun(@(R,C)A(R,C),rows,cols);\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = 1;\r\nB = sub_double(A);\r\nB(1) = 3;\r\nA = 3;\r\nassert(isequal(A,B))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\nB([1 2 3],[3 2 1]) = 0;\r\nA = [1 2 0\r\n     4 0 6\r\n     0 8 9];\r\nassert(isequal(A,B))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\nB([1 3],[3 end]) = [7 7];\r\nA = [1 2 7\r\n     4 5 6\r\n     7 8 7];\r\nassert(isequal(double(A),double(B)))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\ny = B(:,:);\r\ny_correct = [1 5 9];\r\nassert(isequal(y,y_correct))\r\n%%\r\nA = [1 2 3\r\n     4 5 6\r\n     7 8 9];\r\nB = sub_double(A);\r\nB(2:end) = [2:9];\r\nA = A';\r\nassert(isequal(B,A))\r\n%%\r\nA = magic(5);\r\nB = sub_double(A);\r\nB([1 5 4 3 2],[3 4 5 1 2])=0;\r\nassert(isequal(sum(~[B B']),ones(1,10)))\r\n%%\r\nA = magic(7);\r\nB = sub_double(A);\r\nrows = randi(7,1,10);\r\ncols = randi(7,1,10);\r\nvals = randi(7,1,10);\r\nB(rows,cols) = vals;\r\nfor k = 1:10\r\n  A(rows(k),cols(k))=vals(k);\r\nend\r\nassert(isequal(A,B))","published":true,"deleted":false,"likes_count":1,"comments_count":0,"created_by":14358,"edited_by":null,"edited_at":null,"deleted_by":null,"deleted_at":null,"solvers_count":10,"test_suite_updated_at":null,"rescore_all_solutions":false,"group_id":1,"created_at":"2015-01-18T00:53:33.000Z","updated_at":"2026-05-28T04:22:20.000Z","published_at":"2015-01-18T01:36:53.000Z","restored_at":null,"restored_by":null,"spam":false,"simulink":false,"admin_reviewed":false,"description_opc":"{\"relationships\":[{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/document\",\"targetMode\":\"\",\"relationshipId\":\"rId1\",\"target\":\"/matlab/document.xml\"},{\"relationshipType\":\"http://schemas.mathworks.com/matlab/code/2013/relationships/output\",\"targetMode\":\"\",\"relationshipId\":\"rId2\",\"target\":\"/matlab/output.xml\"}],\"parts\":[{\"partUri\":\"/matlab/document.xml\",\"relationship\":[],\"contentType\":\"application/vnd.mathworks.matlab.code.document+xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\"?\u003e\\n\u003cw:document xmlns:w=\\\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\\\"\u003e\u003cw:body\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eMATLAB supports object-oriented programming. Let's take an advantage of it in cody.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eThis problem starts\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:hyperlink w:docLocation=\\\"http://uk.mathworks.com/matlabcentral/cody/problems/2836-class-ics-modify-subscripts-easy\\\"\u003e\u003cw:r\u003e\u003cw:t\u003ehere\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:hyperlink\u003e\u003cw:r\u003e\u003cw:t\u003e.\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"text\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003eLet's take things a bit more seriously. There are\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:i/\u003e\u003c/w:rPr\u003e\u003cw:t\u003esubsasgn\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e and\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e \u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:rPr\u003e\u003cw:i/\u003e\u003c/w:rPr\u003e\u003cw:t\u003esubsref\u003c/w:t\u003e\u003c/w:r\u003e\u003cw:r\u003e\u003cw:t\u003e to overload:\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003cw:p\u003e\u003cw:pPr\u003e\u003cw:pStyle w:val=\\\"code\\\"/\u003e\u003c/w:pPr\u003e\u003cw:r\u003e\u003cw:t\u003e\u003c![CDATA[\u003e\u003e A = sub_double([ 1 4 7\\n                    2 5 8\\n                    3 6 9]);\\n\u003e\u003e A([1 3],[3 1])\\n\\nans = \\n\\n    3x3 sub_double:\\n\\n    double data:    \\n       7    3\\n\\n\u003e\u003e A([1 2 3],[3 2 1]) = 0\\n\\nA = \\n\\n    3x3 sub_double:\\n\\n    double data:\\n       1     2     0\\n       4     0     6\\n       0     8     9\\n\\n\u003e\u003e A(:)'\\n\\nans = \\n\\n    1x9 sub_double:\\n\\n    double data:\\n       1     4     0     2     0     8     0     6     9\\n\\n\u003e\u003e A(:,:)\\n\\nans = \\n\\n    1x3 sub_double:\\n\\n    double data:\\n       1     0     9]]\u003e\u003c/w:t\u003e\u003c/w:r\u003e\u003c/w:p\u003e\u003c/w:body\u003e\u003c/w:document\u003e\"},{\"partUri\":\"/matlab/output.xml\",\"contentType\":\"text/xml\",\"content\":\"\u003c?xml version=\\\"1.0\\\" encoding=\\\"UTF-8\\\" standalone=\\\"no\\\" ?\u003e\u003cembeddedOutputs\u003e\u003cmetaData\u003e\u003cevaluationState\u003emanual\u003c/evaluationState\u003e\u003clayoutState\u003ecode\u003c/layoutState\u003e\u003coutputStatus\u003eready\u003c/outputStatus\u003e\u003c/metaData\u003e\u003coutputArray type=\\\"array\\\"/\u003e\u003cregionArray type=\\\"array\\\"/\u003e\u003c/embeddedOutputs\u003e\"}]}"}],"errors":[],"facets":[[],[{"value":"hard","count":1,"selected":false},{"value":"medium","count":1,"selected":false}]],"term":"tag:\"classics series\"","page":1,"per_page":50,"sort":"map(difficulty_value,0,0,999) asc"}}