CODEWITHSUNDEEP
matlabmatrixcolumn-sum
Prasanna UV
Prasanna UV

Reputation: 41

How do I divide matrix elements by *non-zero* column sums in MATLAB?

I see this question: How do I divide matrix elements by column sums in MATLAB?

But additionally, I want to do the division only if the column sum (sum(A)) is non-zero.
Will any of the listed methods there work, except for the loop-method as it is very slow for my matrix size?

Upvotes: 0

Views: 148

Answers (1)

Shai
Shai

Reputation: 114866

All you need is do remove the zero elements from sum(A) with an intermediate step:

col_sum = sum(A);
col_sum( col_sum == 0 ) = 1; % no zeros

Now you can use any method in the linked post, e.g. using bsxfun:

B = bsxfun(@rdivide, A, col_sum);

From numerical point of view, eliminating only elements that are exactly zero when A is a floating point type, is not a very good practice. Instead you might want to eliminate all close to zero elements:

col_sum( abs(col_sum) < 1e-10 ) = 1;

Upvotes: 1

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