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

Created by William Smith

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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.

Example:

a = [ 1 2 ; 3 5 ];
b = remove_average_vectorized(a);
% b is [ -0.5 0.5 ; -1 1 ];

Solve

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1784 Solutions
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Last Solution submitted on Apr 30, 2025

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9 Comments

9 Comments

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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...

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