Evaluating 2D function on 2D grid without using "for" loops

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Luqman Saleem
Luqman Saleem 2020-8-21
评论： Sara Boznik 2020-8-22
I have a function f(x,y) and I want to evaluate it on x,y grid. For example,
f = @(x,y) x^2+y^2;
x = 1:10;
y = 1:5;
%one way to do it is using for loops.
for x=1:10
for y=1:5
result(x,y) = f(x,y);
end
end
Is there any way do it without using "for" loops?
  1 个评论
Stephen23
Stephen23 2020-8-22
"Is there any way do it without using "for" loops?"
Why do you want to avoid for loops? Contrary to what some beignners think, (well-written) for loops are not slow.
Is result preallocated before the loops?
https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

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回答（1 个）

Sara Boznik
Sara Boznik 2020-8-21
f = @(x,y) x.^2+y.^2;
x = 1:10;
y = 1:5;
[X,Y] = meshgrid(x,y);
meshc(X, Y, f(X,Y))
grid on
You can try that.
Best of luck.
  2 个评论
Luqman Saleem
Luqman Saleem 2020-8-21
Actually, the original function is very large and I will have to put (.) in front of all "^" or "*" operators. It also involves matrix multiplication, so, it will just be very messy if I try to put ".". Is there any way to avoid doing it?

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