# Finding peaks with a set amplitude range?

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HC98 on 10 Feb 2023
Answered: Star Strider on 12 Feb 2023
I'm findint the peaks in a signal wich have an amplitude between 0.2 and 1. Trouble is when I call findpeaks via
[pks,locs] = findpeaks(data(1, :),x); %,x);
logicalIndexes = (pks > 0.8) & (pks < 1);
It just returns a bunch of zeros even though I told it not to. Any ideas?
Dyuman Joshi on 10 Feb 2023
If you have to finding amplitudes between 0.2 and 1, why are you using 0.8?

Mathieu NOE on 10 Feb 2023
hello
see the demo code below :
n = 100;
x= 1:n;
y = rand(1,n);
[pks,locs] = findpeaks(y,x);
logicalIndexes = (pks > 0.8) & (pks < 1);
ind = locs(logicalIndexes);
plot(x,y,x(ind),y(ind),'dr');
Mathieu NOE on 12 Feb 2023
hello again
the x and y values of the peaks as shown above in my demo code are x(ind),y(ind)
n = 100;
x= 1:n;
y = rand(1,n);
[pks,locs] = findpeaks(y,x);
logicalIndexes = (pks > 0.8) & (pks < 1);
ind = locs(logicalIndexes);
plot(x,y,x(ind),y(ind),'dr');

Star Strider on 12 Feb 2023
It just returns a bunch of zeros even though I told it not to. Any ideas?
It may seem that a logical vector is returning zeros (false values, and there may be many zeros in it), however if you use:
NonZeroNr = nnz(logicalIndexes)
to find the number of true values, or:
NumericalIndices = find(logicalIndexes)
to return the subscript indices associated with the true values.
.

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