MATLAB: How can I cancel ("NaN" value) elements of a matrix based on another matrix's "NaN" values?

Question

Let's suppose I have a matrix A=

 1     2     3;
 4     5     6;
 7     8     9

and a matrix B=

1      NaN    3; 
NaN    5      6;  
7      NaN    NaN

I want to cancel the same elements that are canceled in matrix B. It would be:

A2=

 1     NaN     3;
 NaN     5     6;
 7     NaN     NaN

How can I do that?

You can use logical indexing: `A2=A ; A2(isnan(B))=NaN ;` – Hoki Sep 25 '17 at 13:05 — Hoki, Sep 25 '17 at 13:05
@Hoki: Answers in the answers section please. – Bathsheba Sep 25 '17 at 13:10 — Bathsheba, Sep 25 '17 at 13:10

Bathsheba · Accepted Answer · 2017-09-25T13:09:10.880

3

You could create the new matrix A2 such that each element is a2 = b - b + a.

This relies on the fact that NaN propagates through the expression evaluation, and b - b is essentially a no-op in all other instances.

It is also guaranteed never to overflow your type.

edited Sep 25 '17 at 13:09

answered Sep 25 '17 at 12:57

Bathsheba

_a no-op in all other instances_ except if `b = inf` – Luis Mendo Sep 25 '17 at 17:58

1 Answers1