Anonymous function surface plot

Question

Tyrell Wellick 2021-2-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/751704-anonymous-function-surface-plot

编辑： Tyrell Wellick 2021-2-21

Im creating a quadratic form function. Its defined as anonymous function of n-dimensional vector. But when I try to plot it I get an error saying that Z (in surface plot) must be matrix and not a vector. I have n set to 2 but it wont let me plot it. Is there a way to choose have many inputs my anonymous function has?

n = 2;
x_opt = randi([-6,6],n,1);
A = randi(n,n);
T = A*A' + eye(n,n);
h = -T*x_opt;
Q = @(x) 1/2*x'*T*x + h'*x; % n dimensional vector as input
[X,Y] = meshgrid(linspace(-10,10,100));
surf(X,Y,Q,'Edge Color','None') % only 2 dimensional input

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Answer 1

Alan Stevens 2021-2-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/751704-anonymous-function-surface-plot#answer_629244

在 MATLAB Online 中打开

Are you looking for something like this?

n = 2;
x_opt = randi([-6,6],n,1);
A = randi(n,n);
T = A*A' + eye(n,n);
h = -T*x_opt;
Q = @(x) 1/2*x'*T*x + h'*x; % n dimensional vector as input
[X,Y] = meshgrid(linspace(-10,10,100));
Qvals = zeros(size(X));
for i=1:100
   for j= 1:100
      Qvals(i,j) = Q([X(i,j);Y(i,j)]); 
   end
end
surf(X,Y,Qvals,'EdgeColor','None') % only 2 dimensional input