calculate divergence

Hi everyone, I want to calculate divergence of 2-d vector filed A=exp(-(r/alpha)^2).*r. With vector r=x.ux + y.uy (ux: unit vector of x coordinate and uy: unit vector of y coordinate in Cartesian), r=sqrt(x^2 + y^2). alpha is a constant.

This is my code:

v=[-2:0.1:2];

[x,y]=meshgrid(v);

z=x;

r=sqrt(x.^2 + y.^2);

a=r.*exp(-(r./2)^2);

div = divergence(r,a);

contour(v,v,div); hold on;

quiver(div); But I make mistake, I can't write correctly vector A. Can you show me how to correct it? Thanks a lot

Answer 1

[Andrei Bobrov]

so?

a=r.*exp(-(r./2).^2);

[Tuyen Tran]

Thanks for your answer, but do I write vector A in the right way, I don't know if I convert vector r from Cartesian to cyclinder coordinate right or not?