numerical integration

Hi all

I want to numerically integral a function with four variable(f(x,y,z,v)).how can I use dblquad?

[Andrew Newell]

How many variables do you want to integrate over?

[rahman]

I want to integral over all of variables

[Andrew Newell]

Are your integral limits rectangular? e.g., xmin <= x <= xmax?

[rahman]

yes.all of four variables integration domain are limited.

Answer 1

[Andrew Newell]

This turned out to be surprisingly tricky, but here is the solution. First, define a function

function fzv = integrateOverSecondPair(fun,x,y,zmin,zmax,vmin,vmax)

% DBLQUAD evaluates FUN for a vector x and scalar y. The backwards loop is
% Matt Fig's dynamic preallocation.
for ii=numel(x):-1:1
  g = @(z,v) fun(x(ii),y,z,v);
  fzv(ii) = dblquad(g,zmin,zmax,vmin,vmax);
end

Then use the commands

fzv = @(x,y) integrateOverSecondPair(@f,x,y,zmin,zmax,vmin,vmax);
fxyzv = dblquad(fzv,xmin,xmax,ymin,ymax);

[rahman]

tnx Andrew

That work excellent! ;)