Creating a 3D function in Matlab using meshgrid

Question

This should be a really simple question, but for some reason I'm getting unreasonably confused and the Matlab documentation isn't helping.

Given a uniform grid of coordinates (x_i,y_j,z_k), I want to make a 3-dimensional array F in Matlab such that F(i,j,k)=f(x_i,y_j,z_k). The following is obviously incorrect:

x=linspace(-1,1,100)  % uniform mesh on [-1,1]^3
[X,Y,Z]=meshgrid(x);

f=X.*Y.*sin(pi*Y.*Z)   % for example

Do I need to use permute somewhere? I know that I could simply make a triple loop, but as we know that is slow.

Thanks!

Luis Mendo · Accepted Answer · 2014-06-25 09:23:50Z

4

Use ndgrid instead of meshgrid to avoid the unwanted permutation between first and second dimensions.

From the documentation (see also here):

MESHGRID is like NDGRID except that the order of the first two input and output arguments are switched (i.e., [X,Y,Z] = MESHGRID(x,y,z) produces the same result as [Y,X,Z] = NDGRID(y,x,z))

edited Jun 25, 2014 at 9:23

answered Mar 28, 2014 at 21:14

Luis Mendo

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2 Comments

chappjc Over a year ago

Yes, avoid meshgrid when possible! +1 I recently went on a rant about this same thing. So much confusion seems to arise from meshgrid.

Luis Mendo Over a year ago

@chappjc Your rant is well justified I think :-) My favourite one is 'versus .'

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