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## Re: Summation and Mesh Plot

**From**: |
Jordi Gutiérrez Hermoso |

**Subject**: |
Re: Summation and Mesh Plot |

**Date**: |
Wed, 4 Aug 2010 09:18:15 -0500 |

On 29 July 2010 07:08, Anan <address@hidden> wrote:
>
>* I am trying to get the mesh plot which involve a summation.*
>* the code is*
>
>* x=[-4:0.1:4];*
>* y=x;*
>* [xx,yy]=meshgrid(x,y);*
>* fac1=0.0+0.0j;*
>* fac2=0.0+0.0j;*
>* for a=1:10*
>* for c=1:10*
>* fac2=fac2+exp(j*(c-a).*xx);*
>* endfor*
>* endfor*
>* for b=1:10*
>* for a=1:10*
>* fac1=fac1+exp(j*(a-b).*yy)*
>* endfor*
>* endfor*
>* mesh(xx,yy,abs(fac1.*fac2).^2);*
This isn't terrible. You have a few for loops, but they're not slowing
you down noticeably. Here's one way to vectorise this. The trick is
basically that you can delay a few meshgrids and you can use kron to
generate a matrix across which you can sum.
x=[-4:0.1:4];
y=x;
[xx,yy]=meshgrid(x,y);
fac1 = 0;
fac2 = 0;
a = [1:10];
[aa,bb] = meshgrid(a,a);
cc = (bb-aa)(:);
fac1 = sum(exp(j*kron(cc,x)));
[fac2, fac1] = meshgrid(fac1,fac1);
mesh(xx,yy,abs(fac1.*fac2).^2)
HTH,
- Jordi G. H.

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**Re: Summation and Mesh Plot**,
*Jordi Gutiérrez Hermoso* **<=**