Problem 44819. Relative pose in 2D: problem 1

Created by Peter Corke

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483 Solutions
82 Solvers

Last Solution submitted on Jun 09, 2021

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7 Comments

7 Comments

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William on 10 Jan 2019

The test suite needs to call the function, so that the matrix T will be available for testing.

William on 10 Jan 2019

Ooops! I see now that the function is called, but it looks like a program comment "%%T = user_function"

Peter Corke on 12 Jan 2019

That's weird, it shows as a %% comment, but in the problem editor it is not. I've asked MathWorks about this.

goc3 on 17 Jan 2019

A %% needs to be added before the first line. Otherwise, the server parses that first line of the test suite as a comment. I've fixed it here; feel free to fix this problem wherever else it occurs in problems you've created.

Peter Corke on 20 Jan 2019

@goc3 that broke my test! Seems there is some implicit scoping rule, by adding the %% it means that T is not available in subsequent %% cells. Fixed it by calling the user function multiple times. This stuff is not well documented: the scoping rules, the need for a leading %% etc.

goc3 on 25 Jan 2019

Sorry for any confusion that may have been caused. Yes, there may be a need for more detailed explanations of some site functioning, but that is beyond my power. For what it's worth, the scoping rule is consistently applied for all problems on the site: variables called within each test case are only available to that test case. I (and many other problem creators) end up repeating lines for any required variables within each test case.

David Verrelli on 23 Nov 2019

The %% is an issue because it is so poorly documented and hence poorly understood (or even not understood). The following seems to be how it works. [Note: in the following I will use "↲" to indicate the end of a line in the code/output.]

~~~~~~~~~~
Creator writes this TEST SUITE:
~~~~~~~~~~
-----
commandA↲
commandB↲
↲
%% test 1↲
commandX↲
↲
%% test 2↲
commandY↲
-----

~~~~~~~~~~
Cody RUNS the following tests:
~~~~~~~~~~
Test 1: (i) commandA; (ii) commandB; and (iii) commandX.
Test 2: (i) commandA; (ii) commandB; and (iii) commandY.

~~~~~~~~~~
Cody DISPLAYS the following output:
~~~~~~~~~~
-----
%%commandA↲
commandB↲
↲
%% test 1↲
commandX↲
↲
[output from commandX only]↲
↲
%% test 2↲
commandY↲
↲
[output from commandY only]↲
↲
-----
~~~~~~~~~~

Notice: (i) any commands before the first %% [namely commandA and command] are run at the beginning of every test; (ii) output of any commands before the first %% is suppressed [never displayed]; (iii) for the player, a spurious "%%" is displayed on the first line of the Test Suite if there were any commands before the first "%%".

It is actually a very clever structure for Problem Creators writing a Test Suite. Therefore I'd be keen to retain it. See e.g. https://www.mathworks.com/matlabcentral/cody/problems/44655

The annoyances are: (i) lack of documentation; (ii) suppression of output; and (iii) insertion of a spurious "%%" in the display.
Although none of these three issues affect the running, they cause a lot of confusion and misunderstanding.

Solution Comments

Solution 2027627

2 Comments

2 Comments

Zeyue Xia on 16 Aug 2020

I don't really understand where I went wrong. I thought SSW means 202.5 degrees. So, I made 202.5 as my theta.
My matrix was (cos(202.5),-sin202.5,123;sin202.5,cos202.5,-74.6;0,0,1

Khaled Soliman on 19 Aug 2020

Zeyue Xia you should use cosd and sind functions because you've specified the rotation angle in degrees not in radians.
good luck.

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Problem 44819. Relative pose in 2D: problem 1

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Problem 44819. Relative pose in 2D: problem 1

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