Create a matrix with multiple values at each element and apply a function to all?
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This is for optimization purposes - I have 2 linspaces of parameters, and a 2 parameter function f (random values/function):
Xs = linspace(0, 1000, 1000)
Ys = linspace(0, 10000, 10000)
f = @(x, y) cos(x) + sin(y)
I want to populate a matrix M which has size [length(Xs), length(Ys)], where each element of M is f(x, y) for each x in Xs and y in Ys.
I can do this slowly with a for/parfor loop - how can I use direct vectorisation to achieve this?
Thanks
采纳的回答
Steven Lord
2020-4-9
If all the binary operations in your f function support implicit expansion (which is the case for your sample f, as plus supports implicit expansion) call it with vectors of different orientations.
Xs = linspace(0, 1000, 1000);
Ys = linspace(0, 10000, 10000);
f = @(x, y) cos(x) + sin(y);
M = f(Xs.', Ys);
Let's ensure M is the correct size.
isequal(size(M), [length(Xs), length(Ys)]) % true
We can spot-check an element or two of M to ensure it's the same as if we'd called your function with scalar inputs.
check = M(457, 9284) - f(Xs(457), Ys(9284)) % 0 difference
更多回答（1 个）
the cyclist
2020-4-9
Here is one way:
[XXs,YYs] = meshgrid(Xs,Ys);
fxy = f(XXs,YYs);
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