New matrix creation based on 2 existing matrices

I have 2 matrices, a binary matrix representing data points (A) and the other with colour values for each trial (B). Both matrices are equal size. What I am trying to do is create a new matrix that contains the colour value from (B) wherever there is a 1 in (A) and NaN wherever there is a 0.

I am having trouble figure out how to properly map the two matrices together though. I have tried putting C(k,:) = B(k, A==1) in a loop but get an error exceeding dimensions. Also thought C = B(A) might work but it just creates a single column matrix with all the colours in question. I need to the matrix to match the dimensions of the pre-existing matrices.

[Sean de Wolski]

Can you provide sample inputs and the expected results?

Thanks!

Answer 1

[Star Strider]

You’re close, but logical indexing needs to have both sides of the equation have matching indices to work.

This example will do what you want:

A = randi([0 1],10,10)
B = randi([100 107], 10,10)
C = NaN(10);
C(A==1) = B(A==1)

It assumes your colour value is a single scalar quantity. Here, I have numbered the colours [100:107].

[Nick]

Awesome, thanks a lot.

[Star Strider]

My pleasure!