Finding peaks with a set amplitude range?

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]

If you have to finding amplitudes between 0.2 and 1, why are you using 0.8?

Answer 1

[Mathieu NOE]

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');

[HC98]

How can I rewrite this to get peak locations?

I have this

amps = arrayfun(@(h2) max((findpeaks(udata(h2, :), x) < 0.99)...

.* findpeaks(udata(h2, :), x)), 1:size(udata, 1));

And I want to rewrite it to get peak locations. When I call x(amps) it gives a logic error...

[Mathieu NOE]

I am not sure to understand what you are trying to do

what is the context

how is the data / code that you are using here ?

[HC98]

How can I get the corresponding x value for the peaks?

[Mathieu NOE]

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');

Answer 2

[Star Strider]

‘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.

.