I get "Index exceeds matrix dimensions" in Signal Processing

When I try running my function with what was asked from me in my class thhis happens; can someone please help me:

Where S_1 to S_3 are attached

[vel1,corrcoef1] = p2( S_1,S_2,S_3,2048 )

Index exceeds matrix dimensions.

Error in p2 (line 9)

      d1w=detrend(interp(d1(.5*i*fm+1:.5*fm(i+1)),20),'constant');

My code is this:

function [vel,corrcoef] = p2( Ss1,Ss2,Ss3,fm )

%Diferentials especifications

d1=Ss1-Ss2;

d2=Ss2-Ss3;

for i=0:313120

      d1w=detrend(interp(d1(.5*i*fm+1:.5*fm(i+1)),20),'constant');  

      d2w=detrend(interp(d2(.5*i*fm+1:.5*fm(i+1)),20),'constant');  

      [corfun,lags]=xcorr(d1w,d2w);

      fac=sqrt(sum(d1w.^2)*sum(d2w.^2));

      normf=corfun/fac;

      [corrcoef(i+1), pos]=max(normf);

      delay=abs(lags(pos));

     plot(lags,normf);

      vel(i+1)=0.005/(delay/fm);

end

function is attached as well

[Walter Roberson]

What are you passing in as fm? Your .mat file does not contain it.

[Luis Pedro Cobos]

fm is 2048

Answer 1

[Sam Muldoon]

"Index exceeds matrix dimensions" means you tried to access an element of an array either before the array's begining, or more likely, after the array's end.

For example, if A = [1, 2, 3], then A(247) doesn't make very much sense, does it? There are only three elements in the array, how on earth could you access a 247th element of it?

247 is the "index." The dimensions of A are one row, and three columns. The index exceeds the matrix dimensions.

[Luis Pedro Cobos]

I have no 247 anywhere on my code

[Stephen23]

@Sam Muldoon: +1 for a clear explanation and example.

Answer 2

[Walter Roberson]

Your code has

   d1w=detrend(interp(d1(.5*i*fm+1:.5*fm(i+1)),20),'constant');

Notice the fm(i+1) . That is a request to index fm at position i+1 . Perhaps you omitted a multiplication,

   d1w=detrend(interp(d1(.5*i*fm+1:.5*fm*(i+1)),20),'constant');

[Luis Pedro Cobos]

That was it thanx!!!!