Write a for/while loop with "if/else" in a more elegant way?

Question

I've written this code :

A is a nXm matrix

[nA, mA] = size(A); currentVector(nA,mA) = 0; for i = 1: nA for j = 1 : mA if A (i,j) ~= 0 currentVector(i,j) = ceil(log10( abs(A(i,j)) )); else currentVector(i,j) = 0; end end end

How can I write the above code in a more "matlab" way ?

Are there any shortcuts for if/else and for loops ? for example in C :

int a = 0; int b = 10; a = b > 100 ? b : a;

Those if/else conditions keeps reminding me of C and Java .

Thanks

Amro · Accepted Answer · 2012-06-02 05:30:39Z

5

%# initialize a matrix of zeros of same size as A currentVector = zeros(size(A)); %# find linear-indices of elements where A is non-zero idx = (A ~= 0); %# fill output matrix at those locations with the corresponding elements from A %# (we apply a formula "ceil(log10(abs(.)))" to those elements then store them) currentVector(idx) = ceil(log10( abs(A(idx)) ));

edited Jun 2, 2012 at 5:30

answered Jun 2, 2012 at 5:24

Amro

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3 Comments

Kijewski Over a year ago

Best solution, but I guess you should put some explanation. ;-)

Amro Over a year ago

@kay: done. Feel free to add references to relevant sections in the MATLAB documentation (I'm sure there are plenty discussing writing vectorized code, and performing matrix indexing)

JAN Over a year ago

@Amro: Amazing, I'll use that from now on . Thanks!

Serg · Accepted Answer · 2012-06-03 15:26:59Z

currentVector = ceil(log10(abs(A))); currentVector(A == 0) = 0;

Note: in Matlab it is totally legal to apply log on zeros - the result is: -inf.

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