Problem 963. We love vectorized solutions. Problem 1 : remove the row average.

Created by William Smith

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>Given a 2-d matrix, remove the row average from each row. Your solution MUST be vectorized. The solution will be tested for accuracy AND speed. Any for loops will make the solution too slow to pass the speed test.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Example:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[a = [ 1 2 ; 3 5 ];\nb = remove_average_vectorized(a);\n% b is [ -0.5 0.5 ; -1 1 ];]]></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>"}]}

Solve

Solution Stats

1648 Solutions
761 Solvers

Last Solution submitted on Mar 30, 2023

Last 200 Solutions

Problem Comments

9 Comments

9 Comments

Show 6 older comments

Richard Zapor on 2 Oct 2012

Please modify the fourth test suite so it reports the duration when the assert fails. My tests say I should pass but Cody is exceeding the time. The method to output information on a failed assert is: assert(duration<2,sprintf('Time used %2.3f\n',duration));

thx

Richard Zapor on 2 Oct 2012

The other thing to do is to remove the ";" from the duration=toc(timer) line. This will allow everyone to see how fast the successful routines take to execute. My self-test times are < 500msec but I don't know Cody's speed. thx

William Smith on 2 Oct 2012

Thanks Richard, your suggestions have been implemented.

William Smith on 2 Oct 2012

I am hoping to stimulate a change to cody where some problems (or all) problems are graded on performance not size. A low size often means an unreadable solution, and people have found enough tricks to make size an irrelevance, anyway.

David Verrelli on 25 May 2018

As per Solution 1539945, the Test Suite has been corrupted for me. For me the first line of the Test Suite appears to read "%%x = [ 0 1 ; 2 3 ] ;", and the correct inputs are not supplied. This may be the same Cody bug that previously affected Problem 970 (& perhaps Problem 1319) and still affects Problem 753.

Stephen Little on 23 Apr 2019

Timing aspect is neat.

Rafael S.T. Vieira on 23 Jul 2020

The solution with for is able to solve this problem currently within time. When requesting performance, you should measure the time dynamically, or else you will be forced to adjust the threshold as the years go by and computers evolve.

Rik on 2 Mar 2021

You should make the timing test dynamic. The current optimally vectorized solution is about 7 or 8 times faster than the default looped solution. You could add a test that confirms at least a 75% time reduction.

Vladimir Socha on 15 Oct 2022

This was pretty easy...

Solution Comments

Solution 2730651

1 Comment

1 Comment

Rafael S.T. Vieira on 23 Jul 2020

Btw, I've sent this solution before submitting the default solution. Since this was pretty fast, I guessed that the default would work too.

Solution 1950456

1 Comment

1 Comment

Cailean MacLabhruinn on 12 Dec 2022

How can this be the leading "solution"? I see that it passes the tests but it is not a solution.

Solution 1705059

1 Comment

1 Comment

Joanne Marsh on 9 Jan 2019

Not sure why this is not passing, I've tested time and it completes under 1 second... Anyone have any ideas?

I'm getting the error "While evaluating the solution, the server encountered an error caused by temporary unavailability of MATLAB Service. Wait a few minutes for the MATLAB Service to return, and then rescore." but have been able to submit other answers so I assuming it is not passing?

Solution 1700984

1 Comment

1 Comment

Nikolaos Nikolaou on 31 Dec 2018

By vectorized he means y=[..... ] ? Or is it just bugged so this is futile?

Solution 1541085

3 Comments

3 Comments

David Verrelli on 27 May 2018

There is a serious problem with the Test Suite for this submission to pass!!! —DIV

David Verrelli on 27 May 2018

26–27 May 2018: 2L. Time used = 1.115 seconds in last test case.

David Verrelli on 27 May 2018

See Problem 44655. https://www.mathworks.com/matlabcentral/cody/problems/44655

Solution 1541083

1 Comment

1 Comment

David Verrelli on 27 May 2018

Consistently, reproducibly getting the following error, "While evaluating the solution, the server encountered an error caused by temporary unavailability of MATLAB Service. Wait a few minutes for the MATLAB Service to return, and then rescore." only for certain array assignments to variable y. See submission code. —DIV

Solution 1539945