Vectorization of a Value function
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I have a function of 3 variables, say A(x,y,z), that I represent as 3D object. (x,y,z are elements of a grid)
Suppose z is also function of x,y, say z(x,y) and I want to evaluate V(x,y) = A(x,y,z(x,y)). (Where z is the relevant index of the grid)
How do I do this? Obviously I can do this easily with a loop, but is there a better answer?
Btw, the way I am doing it now is like this
for i_y=1:Ny
for i_r = 1:Nr
for i_d =1:Nd
for i_w = 1:Nw
V(i_y,i_r,i_d,i_w)= A(i_y,i_r,i_d,i_w, Z(i_y,i_r,i_d,i_w));
end
end
end
end
2 Comments
Muthu Annamalai
on 8 Oct 2012
Sergio, you need to look at meshgrid() function. This provides an easy way to get solution to the problem of vectorially calculating A(x,y,Z(x,y)) or in steps as Julien suggests.
[XX,YY] = meshgrid(x,y); %x,y can be 1D vectors here
Now XX,YY correspond to grid points (XX(1),YY(1)) etc.
Once you have meshgrid just directly evaluate your function, and it will have all the values across the X-Y grid.
Accepted Answer
Andrei Bobrov
on 8 Oct 2012
ii = cell(1,4);
[ii{:}] = ndgrid(1:Ny,1:Nr,1:Nd,1:Nw);
v = cellfun(@(x)x(:),ii,'un',0);
V = zeros(size(ii{1}));
V(v{:})= A(v{:}, Z(v{:}));
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