Select values in the matrix based on the condition

Hi,

I have two matrix A and B of 94349 x 1.

Here the values in the matrix A are range from 0 to 1. First, I have to identify row numbers in the matrix A that got values only in the range of 0.05 to 0.06. Then I have to read values from matrix B that pertains to only the preselected rows from step 1.

Answer 1

[NIVEDITA MAJEE]

Hi,

You could do the following:

filtered_idx = find((A>=0.05 & A<=0.06)) %this will store the indexes from the matrix A which have values between 0.05 and 0.06
filtered_B = B(filtered_idx) %this will store the values corresponding to the indexes stored in filtered_idx

Hope this helps!

[Steven Lord]

You don't care where the items in the desired range are located, all you care is that you can select them. So you don't need find.

x = 1:10;
logicalMask = (4 <= x) & (x <= 7)

logicalMask = 1×10 logical array
   0   0   0   1   1   1   1   0   0   0

linearIndices = find(logicalMask)

linearIndices = 1×4

4 5 6 7

You can use either the logical mask or the linear indices to obtain the values from x. But you can see that calling find is a second step beyond generating the logical mask, so if you don't actually need the linear indices why compute them?

x(logicalMask)

ans = 1×4

4 5 6 7

x(linearIndices)

ans = 1×4

4 5 6 7