Is there a function that returns a vector or array or list of values obtained by applying a function to margins of an array or matrix?

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Bruno Remillard
Bruno Remillard 2015-7-9
编辑： James Tursa 2015-7-10
For example, assume x is a vector of length n, and y is a vector of length m. I would like to construct the matrix the (n x m) matrix M(i,j) = f(x(i),y(j)). Of course I do not want to use loops!
Btw, in R, there is such a function (called apply).

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Image Analyst
Image Analyst 2015-7-9
Use meshgrid()
[X, Y] = meshgrid(x,y);
M = f(X, Y);
You might need to use reshape() after that to make M be 2D
M = reshape(M, m, n);
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Image Analyst
Image Analyst 2015-7-10
You need to be careful. meshgrid() works on x and y, while other functions, like reshape() work on rows and columns. Note, you used x and y and said x had n columns and y had m rows. However you said that M was nxm, meaning n rows and m columns, which is the reverse. So you either made the very common mistake of thinking (rows,columns) was the same as (x,y) or you intentionally thought that your "f" function would do a transpose. Either way, you just have to be careful.

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James Tursa
James Tursa 2015-7-9
编辑：James Tursa 2015-7-9
A bit clunky, but this works and makes no assumptions about f being vectorized:
n = numel(x);
m = numel(y);
M = arrayfun(@f,repmat(x(:),1,m),repmat(y(:)',n,1));
John D'Errico
John D'Errico 2015-7-9
I'm surprised nobody mentioned this.
fun = @(x,y) sin(x+y);
x = 0:5;
y = (0:2:6)';
M = bsxfun(fun,x,y)
M =
0 0.84147 0.9093 0.14112 -0.7568 -0.95892
0.9093 0.14112 -0.7568 -0.95892 -0.27942 0.65699
-0.7568 -0.95892 -0.27942 0.65699 0.98936 0.41212
-0.27942 0.65699 0.98936 0.41212 -0.54402 -0.99999
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James Tursa
James Tursa 2015-7-10
编辑：James Tursa 2015-7-10
I guess I wasn't clear. bsxfun passes column vectors to the function, so whatever the function is, it must be able to deal with column vector inputs (i.e., it must be vectorized to this extent). That was the only point I was trying to make. It is similar to the f(X,Y) used in IA's solution ... f must be vectorized for this to work.

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