Error in findpeaks when trying to find the x corodinate

Hello,

I have been testing out the "findpeaks" function and have found that when I use:

[pks,locs] = findpeaks(a),

The Y value of the peaks is correct, but the locs value is just the indices.

Then I use

[pks,locs] = findpeaks(a,t)

I get the following error:

Error using findpeaks>parse_inputs (line 131)
Expected a string for the parameter name, instead the input type was 'double'.

Error in findpeaks (line 71)
[X,Ph,Pd,Th,Np,Str,infIdx] = parse_inputs(Xin,varargin{:});

Error in Damping (line 36)
   [pks,locs] = findpeaks(a,t);

I have looked online for some solutions and have found that I get the same error when using this script from this thread: http://www.mathworks.com/matlabcentral/answers/158309-how-to-find-the-peaks-both-x-and-y-location

% Create the sample data
x = linspace(0,1,1000);
Pos = [1 2 3 5 7 8]/10;
Hgt = [4 4 4 2 2 3];
Wdt = [2 6 3 3 4 6]/100;
for n = 1:length(Pos)
    Gauss(n,:) =  Hgt(n)*exp(-((x - Pos(n))/Wdt(n)).^2);
end
PeakSig = sum(Gauss);
plot(x,Gauss,'--',x,PeakSig)
% Use findpeaks with default settings to find the peaks of the signal and their locations.
[pks,locs] = findpeaks(PeakSig,x)
% Plot the peaks using findpeaks and label them.
findpeaks(PeakSig,x)
text(locs+.02,pks,num2str((1:numel(pks))'))
% Sort the peaks from tallest to shortest.
[psor,lsor] = findpeaks(PeakSig,x,'SortStr','descend');
findpeaks(PeakSig,x)
text(lsor+.02,psor,num2str((1:numel(psor))'))

but I still get the same error:

Error using findpeaks>parse_inputs (line 131)
Expected a string for the parameter name, instead the input type was 'double'.

Error in findpeaks (line 71)
[X,Ph,Pd,Th,Np,Str,infIdx] = parse_inputs(Xin,varargin{:});

Error in Testpeask (line 12)
[pks,locs] = findpeaks(PeakSig,x)

does this mean there is something wrong with my matlab?

Thanks for your help

[Maximilian Weber]

How did you fix this? I'm also stuck with the same error:

Error using findpeaks>parse_inputs (line 288)
Expected a string scalar or character vector for the
parameter name, instead the input type was 'double'.
Error in findpeaks (line 136)
  = parse_inputs(isInMATLAB,Yin,varargin{:});
Error in f0est (line 81)
    findpeaks(specdb,npartials,'MinPeakWidth',minpeakwidth,'MaxPeakWidth',maxpeakwidth,...

Answer 1

[Thorsten]

 [pks,locs] = findpeaks(PeakSig);
 plot(x, PeakSig)
 text(x(locs)+.02,pks,num2str((1:numel(pks))'))

Sorted according to height

[pks ind] = sort(pks, 'Descend');
locs = locs(ind);
text(x(locs)+.02,pks,num2str((1:numel(pks))'))

[Alexander]

Thanks for your help, with it I managed to get the sample script working, however this still doesn't give me the x values in a vector. I was just looking at my matlab help, and it seems that the findpeaks function no longer supports finding the x value, can you confirm this?

And if so, do you know any other way of finding them with the use of a matlab script (non-manual)

Thanks again for your help

[Adam]

If t is where you want to get the x values from then simply

t(ind);

will map those indices into your t vector to give you the locations.

[Thorsten]

Like Adam said. In your case you get the x values with

x(locs)

locs give you the index of the peaks, so x(locs) gives you the values of the corresponding x positions.

[Alexander]

You are amazing. Thank you very much!

[Thorsten]

My pleasure :-)