Problem 45218. Find a common edge

Created by Nicolas Douillet

Solve Later

{"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":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>First input is T, a triplet list of indices. Second input is e = [e1 e2], a row vector, couple of indices (positive distinct integers always sorted in ascending order, ie</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:b/></w:rPr><w:t>e1 &lt; e2</w:t></w:r><w:r><w:t> ). The goal of this function is to find and return the indices of the rows in the list which contain this particular edge. Output format can be either a column or a row vector.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>For example if inputs are</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[T = [1 2 3 ;\n 1 3 4 ;\n 1 4 2 ;\n 2 3 4]]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>and</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[e = [2 3]]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>the output is the vector</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[row_idx = [1 4]]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>since [2 3] is contained in rows number 1 and 4 of T. With the same input T, but with e = [2 4] this time, the output is the vector row_idx = [3 4], since [2 4] is contained in rows number 3 and 4 of T (Note that</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:b/></w:rPr><w:t>edge [b a] is the same as edge [a b]</w:t></w:r><w:r><w:t> so must be the corresponding outputs). If the edge is not in the list, the function must of course return the empty set.</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

First input is T, a triplet list of indices. Second input is e = [e1 e2], a row vector, couple of indices (positive distinct integers always sorted in ascending order, ie e1 &lt; e2 ). The goal of this function is to find and return the indices of the rows in the list which contain this particular edge. Output format can be either a column or a row vector.For example if inputs are<pre class="language-matlab">T = [1 2 3 ;
 1 3 4 ;
 1 4 2 ;
 2 3 4]
</pre>and<pre class="language-matlab">e = [2 3]
</pre>the output is the vector<pre class="language-matlab">row_idx = [1 4]
</pre>since [2 3] is contained in rows number 1 and 4 of T. With the same input T, but with e = [2 4] this time, the output is the vector row_idx = [3 4], since [2 4] is contained in rows number 3 and 4 of T (Note that edge [b a] is the same as edge [a b] so must be the corresponding outputs). If the edge is not in the list, the function must of course return the empty set.

Solve

Solution Stats

31 Solutions
16 Solvers

Last Solution submitted on Dec 04, 2022

Last 200 Solutions

Problem Comments

1 Comment

1 Comment

Nicolas Douillet on 1 Dec 2019

Info : T is actually a triangulation -list of triangles-, in which each index corresponding to the row index of a vertex in another list -a vertices list-, it is a widely used technique used to store and write triangular meshes in mesh processing. Here below the example is a tetrahedron -4 facets-.

Problem Recent Solvers16

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 45218. Find a common edge

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers16

Suggested Problems

More from this Author9

Problem Tags

Community Treasure Hunt

Problem 45218. Find a common edge

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers16

Suggested Problems

More from this Author9

Problem Tags

Community Treasure Hunt

Players