Not able to detect the peak for randon signal

function [maxtab, mintab]=peakdet(v, delta, x)

maxtab = [];
mintab = [];

v = v(:); % Just in case this wasn't a proper vector

if nargin < 3
  x = (1:length(v))';
else 
  x = x(:);
  if length(v)~= length(x)
    error('Input vectors v and x must have same length');
  end
end

if (length(delta(:)))>1
  error('Input argument DELTA must be a scalar');
end

if delta <= 0
  error('Input argument DELTA must be positive');
end

mn = Inf; mx = -Inf;
mnpos = NaN; mxpos = NaN;

lookformax = 1;

for i=1:length(v)
  this = v(i);
  if this > mx, mx = this; mxpos = x(i); end
  if this < mn, mn = this; mnpos = x(i); end

    if lookformax
      if this < mx-delta
        maxtab = [maxtab ; mxpos mx];
        mn = this; mnpos = x(i);
        lookformax = 0;
      end  
    else
      if this > mn+delta
        mintab = [mintab ; mnpos mn];
        mx = this; mxpos = x(i);
        lookformax = 1;
      end
    end
  end

   I am using this code for detecting the peak and valley in the signal. But whenever i and giving some random signal it is giving error that vector length should be same.
 e g i generate following random signal

> sig_length = 20; sig = rand(1,sig_length);

 [c,d]=peakdet(sig,1,sig_length)
??? Error using ==> peakdet at 29
Input vectors v and x must have same length

Can anybody help me out why this error is coming even if length of v and x is same.

Regards Jeevan Patil

Answer 1

[Wayne King]

Hi, Because you have this code at line 9:

if length(v)~= length(x)

But sig and sig_length are not equal in length. sig is a vector, and sig_length is a scalar, so the length of sig_length is 1.

Perhaps you meant to write in the code

if (length(v) ~= x)

I don't know if that alone makes the code work, but I do see that the code is currently written so that v and x are the same length.

[Jeevan Patil]

Thanks Wayne King... I got it.