Plotting 2-variable Function with integration using MatLab

Question

Ganna 2014-9-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/155458-plotting-2-variable-function-with-integration-using-matlab

回答： Youssef Khmou 2014-9-19

Does anyone have an example of how to plot a 2-variable function with integration in MatLab (without using MuPAD)?

Here is what I've got:

clear all;

%define a, p and w

a=1; p=1; w=5;

%calculate xmin and xmax

xmin=a-p/2 xmax=a+p/2

%define the coordinates

x=linspace(xmin,xmax); y=linspace(0,1);

%define the coordinates along x-y plane

[x,y]=meshgrid(x,y);

%define and compute the given function along the x-y coordinates

z=w-(1/p)*int((x.-y)^2, x, xamin, xmax) ;

figure surf(y,x,z) title ('a=1 and p=1'); xlabel('w') ylabel('t') zlabel('x') axis tight shading interp colorbar

Clearly, there is something wrong with my function z. The function is

z=w-(1/p)*int(x-t)^2dx where x ranges from a-p/2 to a+p/2

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Answer 1

Youssef Khmou 2014-9-19

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https://ww2.mathworks.cn/matlabcentral/answers/155458-plotting-2-variable-function-with-integration-using-matlab#answer_152272

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The problem is in the function int, it is designed for symbolic calculation while your work with numerical one, if you have the function integral you try the following :

   clear all;
a=1; p=1; w=5;
xmin=a-p/2; xmax=a+p/2;
x=linspace(xmin,xmax); y=linspace(0,1);
[x,y]=meshgrid(x,y);
L=integral((x-y)^2,1/length(x));
z=w-(1/p)*(L) ;
figure; surf(x,y,z); title('a=1 and p=1'); xlabel('w');ylabel('t');zlabel('x');