Problem 42504. Data Regularization

Created by Peng Liu

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Provided is an m-by-n integer data matrix A whose elements are drawn arbitrarily from a set S = [1,2,3,...,S] for any large integer number S &gt; 1. The "arbitrary" manner of drawing integer numbers implies that each column of A might contain only a subset of integer numbers from S. Our objective is to regularize the data in A subject to the following rules:For each column in A,<ul><li>The smallest number or numbers (if there are more than one such number) are mapped to 1;</li><li>The 2nd-smallest number or numbers (if there are more than one such number) are mapped to 2;</li><li>The k th-smallest number or numbers (if there are more than one such number) are mapped to k .</li></ul>For example, S = [1:8] with S = 8. Suppose the input data matrix A is<pre class="language-matlab">A = [2 6
 5 3
 5 6
 3 7]
</pre>Then the output matrix B is<pre class="language-matlab">B = [1 2 
 3 1
 3 2
 2 3]
</pre>Please try to avoid for or while loops. Vectorized code will be more appreciated.

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120 Solutions
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Last Solution submitted on Oct 18, 2021

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3 Comments

Asif Newaz on 12 May 2020

without loop makes it quite difficult..is there any particular built-in function to do this?

Rafael S.T. Vieira on 29 Jun 2020

You do know that Matlab most certainly uses while and for loops to multiply matrices internally. The vectorized solution is probably faster because of parallelization and other optimization tricks, which we could also implement with the proper toolboxes.

Rafael S.T. Vieira on 29 Jun 2020

And please add an space to strfind, or else It will find fors and whiles inside comments and even parameter names. I was using a parameter "Uniform" of the function cellfun and it took me a while to realize why it was failing the first test.

Solution Comments

Solution 714294

1 Comment

1 Comment

Peng Liu on 13 Aug 2015

very nice idea!

Solution 713866

1 Comment

1 Comment

Peng Liu on 12 Aug 2015

The first truly vectorized solution I've seen here without using for, while, cellfun, arrayfun, etc.

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integer matrix vectorization

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Problem 42504. Data Regularization

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Problem 42504. Data Regularization

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