trying to find peaks on a time series

i'm trying to find peaks on some time series data but when i write

[pks,locs]=findpeaks(x)

i get the position of peak on locs. but i want to get the locs the same length i have x files or better if i have locs represented as 0 and 1 i can get the x values without a hassle. is there an elegant and simple way of dooing it, like the find function??

i also am trying this but obviously it takes time because of the loops, is there any simple way of dooing this in matlab.

newx=zeros(length(xn),1);
for p=1:length(xn);
  for m=1:length(locs);
      if locs(m)==p
          newx(p)=1;
      else
      end;
  end;
end;
end;

[Ryan]

I am confused, if you have the locations of the peaks already, what is the issue? What type of location information is stored in locs?

[DuckDuck]

look at my code, i want to know if there is a better way of writing that code, because loops take a long time in matlab

Answer 1

[Wayne King]

I'm assuming that xn in your loop above is the signal. You don't show us where xn comes from and it's not used in your call to findpeaks(). In your call to findpeaks, you use x. So If that is the case, then you don't need a loop.

 newx = zeros(size(x));
 newx(locs) = 1;

Does the same thing as your loop.

[DuckDuck]

yeah you are right, basically xn is s x.

no it does not, i tried and it did not.

Answer 2

[Wayne King]

Then please compare:

x = [2 12 4 6 9 4 3 1 19 7];
[pks,locs] = findpeaks(x);

% here is your code
newx=zeros(length(x),1);
for p=1:length(x);
  for m=1:length(locs);
      if locs(m)==p
          newx(p)=1;
      else
      end
  end
end

Now what I answered:

newx2 = zeros(length(x),1);
newx2(locs) = 1;

Now

isequal(newx,newx2)

That returns a 1 for me.