How to find column and row indexes of items that are +-inf or Nan ?

Hello

I have a very large matrix X where some elements can be -+inf or Nan. Currently I loop over all elements, check each one and handle it. It is taking forever. How can I easily find the [row,col] coordinates of such items ? I tried fiddling with isfinite(X) but in vain

Thanks much for any help

Answer 1

[Azzi Abdelmalek]

A=[inf 1 4 nan;4 -inf 2 nan]; % Example
[ii,jj]=find(isnan(A)| isinf(A))

You can also use logical indexing, which is faster

idx=isnan(A)| isinf(A)

[tci27]

Thanks much, got it, working some 1000 times faster than before :)

Answer 2

[Jos (10584)]

Using ISFINITE is fine. You just have to negate the outcome

Here is a small example, showing all the steps:

M = [1 Inf 3 ; 11 12 NaN]
tf = isfinite(M)
tf = ~tf
[ri,ci] = find(tf)

which you can combine into a single line if you understand each step

[ri,ci] = find(~isfinite(M))

[Jan]

Fixed typo: "INFINITE" => "ISFINITE".

[Jos (10584)]

thanks Jan

Answer 3

[rui gao]

Hi. If I need omit these elements (inf) to calculate the variance, how to achieve it?