To 3Dplot a function that is inside a nested for loop

Question

Martins Jancevskis 2019-9-1

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/478469-to-3dplot-a-function-that-is-inside-a-nested-for-loop

回答： Star Strider 2019-9-1

I am trying to plot a 3D figure out of 2D gaussian function 'z' . I need to plot the z values as a 3D plot

clear all;
clc;
XMin = -2.5;
XMax = 2.5;
YMin = XMin;
YMax = XMax;
increment = 0.01;
sigma = 1;
for x = XMin:increment:XMax
    for y = YMin:increment:YMax
        z = exp((-((x.^2)+(y.^2))./2)*(sigma.^2));
    end
end
% Trying to plot a 3D figure

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Answer 1

Star Strider 2019-9-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/478469-to-3dplot-a-function-that-is-inside-a-nested-for-loop#answer_389984

在 MATLAB Online 中打开

You are not saving the values of ‘z’ in your loop as a matrix.

However there is a more efficient way to do what you want, avoiding the (explicit) loops entirely:

XMin = -2.5;
XMax = 2.5;
YMin = XMin;
YMax = XMax;
increment = 0.01;
sigma = 1;
Xv = XMin:increment:XMax;                                       % Assign Vector
Yv = YMin:increment:YMax;                                       % Assign Vector
z = @(x,y) exp((-((x.^2)+(y.^2))./2)*(sigma.^2));               % Anonymous Function (For Ceonvenience)
[Xm,Ym] = ndgrid(Xv,Yv);                                        % Generate Grid Matrices
figure
surf(Xv, Yv, z(Xm,Ym), 'EdgeColor','none')                      % Evaluate & Plot
grid on