Setting a logical matrix to a number

Sorry if this has been posted before - but I couldn't find anything similar!

I have a matrix 176x80, and I've found the local max values which has given me a logical array of the same size

Now I want to change each true value to a certain number on a scale. I defined for the vector for this, and thought I'd need to use a loop - the loop technically works but not in the way I want;

for k=1:14080
if TF_com(k) >= 0.1
   TF_com(k)=wavenumber(k);
else TF_com(k)=0;
end
end

Essentially, I want each true value in TF_com to become a wavenumber. However, when I run the code instead of listing the true values in order of wavenumber i.e.

true = wavenumber(1), false = 0, false = 0, true = wavenumber(2)

the loop makes the false values a wavenumber but still shows them as zero

I've tried to add a loop inside, but most of the time I get the error 'arrays don't match in size'

If it helps I know that there are 806 true values, where each one is a different wavenumber

Thanks!!!

Answer 1

[dpb]

A logical array is either 0 or 1...if you put something else in an element, then the array can no longer be class logical

You can do the assignment just using the logical addressing vector, but result will have to be a numeric array.

WN_ary=zeros(size(TF_com));       % Preallocate
idxNZ=find(TF_com);               % the nonzero locations
WN_ary(idxNZ)=wavenumber(idxNZ);  % store the NZ location values

[Frances Roberts]

Thank you!!

I think I orginally tried to do this but got a bit confused! I made a slight modification so the numbers would go in order, but otherwise it works!!

WN_ary=zeros(size(TF_com));       
idxNZ=find(TF_com);               
WN_ary(idxNZ)=wavenumber(1:806,1);

[dpb]

That's NOT the same solution as what you wrote originally...that doesn't put the wave number associated with the location in the location but just the 1:N values.

If that is what you really intend, ok, but make sure it really is the correct solution. And, if it that is so, don't bury "magic numbers" like 806 in the code, use something like

WN_ary(idxNZ)=wavenumber(1:numel(idxNZ));

instead so you don't have to change the code if the data change.