MATLAB Answers

Anonymous function surface plot

60 views (last 30 days)
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

Accepted Answer

Alan Stevens
Alan Stevens on 21 Feb 2021
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
  1 Comment
Tyrell Wellick
Tyrell Wellick on 21 Feb 2021
Yes. Thank you very much. I forgot that the Q is only a function. And the surface plot needs actual values from the grid.

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!