index exceeds matrix dimension

i am getting an error in the code to find peaks. Actually finding peaks is a function I am using for my main program to synchronize two files with respect to the time of the 2 files.

% pkind= index of the peak values % vlyind= index of valley % ind=index of sample when synch signal changes from hours to seconds

%% Peak Detection a=0; max = []; min = []; delta=0.15; % change this threshold if the peaks are not detected correctly d1=smooth(a); d2=1:length(d1); mn = 0; mx = 0; mnpos = 0; mxpos = 0;

lookformax = 1;

for i=1:length(d1) a1 = d1(i); if a1 > mx, mx = a1; mxpos = i; end if a1 < mn, mn = a1; mnpos = i; end

if lookformax
  if a1 < mx-delta
    max = [max ; mxpos mx];
    mn = a1; mnpos = i;
    lookformax = 0;
  end  
else 
  if a1 > mn+delta
    min = [min ; mnpos mn];
    mx = a1; mxpos = i;
    lookformax = 1;
  end
end
end

v1=max(:,2); v2=min(:,2); index=max(:,1); index2=min(:,1); t1=d2(index); t2=d2(index2); figure plot(d2,d1);hold on plot(t1,v1,'*r');hold on plot(t2,v2,'*r');hold off

The error is in v1,v2, index and index2. I am new to MATLAB and donot know the different functions which I could use or commands to handle the matrix dimension issue. I would be grateful if I could get some suggestions.

Answer 1

[John Petersen]

First of all, it's probably not a good idea to use reserved words for variable names, such as max and min. These are standard function calls in matlab. You can type

>>help max

for example, to see if it is reserved.

Where does the data go? You have what seems to be the data in "a" but it's initialized to 0 and never changes. So you'll never find a max or min and all your vectors will remain empty. When you try to index into an empty array, you will get an error message.