Help on speed optimization of convolution code

I want to calculate the convoluted value of a quantity based on the relationship

c(x) = integral (crs(x')*abs(x')dx') / integral (abs(x')*dx'),

actually it is the convolution of a spectrum (crs in my case) with a slit funtion (abs respectively).

I have "translated" a code i had made in the past in vb to matlab, it works fine but it is very slow, so i am asking any help/advice for speed optimization.

My code is below

w1=-1.5;
w2=1.5;
for ii=1:size(w_sl) %size = 6
for w=w_sl(ii)-1.5:0.01:w_sl(ii)+1.5
  sf=0;
  z=0;
  for j=1:size(wv,1) % size = 1956
    if wv(j)>w+w1 && wv(j)<w+w2  
    for l=1:size(Slit005,1)
      if wv_sl(l)==wv(j)-w % if wavelength match exactly then 
        z=z+crs(j)*abs(l); %calculate the integral (sum) of spectrum + slit function
        sf=sf+abs(l);
        break
      end
      if wv_sl(l)>wv(j)-w %if wavelength doesn't match exactly then interpolate slit function to current wavelength
        yint=(abs(l)*(wv(j)-w-wv_sl(l-1))-abs(l-1)*(wv(j)-w-wv_sl(l)))/(wv_sl(l)-wv_sl(l-1));
        z=z+crs(j)*yint;
        sf=sf+yint;
        break
      end
    end
    end
  end
  if sf>0
  m=m+1;
  crs_O3(m,:)=[w z/sf];
  end
end
end

Thank you very much

Answer 1

[Andrew Newell]

You could probably speed it up considerably by using the MATLAB function filter (see also Filter Implementation and Analysis).

Note that abs is the name of a MATLAB builtin function, so you shouldn't use it for a variable name.

[Andrew Newell]

Unfortunately i didn't manage to implement, i am not just new in matlab answers but in matlab in general, so the way i am programming is much more different than matlab.. but to be totally honor i didn't search it very much. I must finish some tasks till the end of the month so for the moment, unfortunately, i can't afford time working on new techniques (i was expecting that somebody could provide an optimization on my posted code), i keep your answer in my mind so as to search on it in the near future. Sure conv2 function that imageanalyst suggested doesn't work for what i need to do, so i 'll vote your answer.

Answer 2

[Image Analyst]

Just use the built-in function "conv2" - it's already highly optimized.