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

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tci27
tci27 2013-7-18
回答： rui gao 2018-11-25
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

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Azzi Abdelmalek
Azzi Abdelmalek 2013-7-18
编辑：Azzi Abdelmalek 2013-7-18
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)

更多回答（2 个）

Jos (10584)
Jos (10584) 2013-7-18
编辑：Jan 2013-7-18
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))
rui gao
rui gao 2018-11-25
Hi. If I need omit these elements (inf) to calculate the variance, how to achieve it?

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