Plot functions and intersections

Question

Harel Harel Shattenstein 2019-5-27

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464251-plot-functions-and-intersections

回答： Star Strider 2019-5-27

在 MATLAB Online 中打开

Hi,

I am trying to plot a feasble area of a LP problem:

Max z=2*x1+2*x2

s.t

2*x1+x2 <= 16

3*x1+2*x2 <=25

2*x1+3*x2 <=25

x1+x2<=16

x1,x2>=0

I started with ploting the functions alone (without intersection points), but it seems that fplot does not work with multpile variables

fun1 = @(x1,x2) 2*x1 + x2 == 16;
fun2 = @(x1,x2) 3*x1 + 2*x2 == 25;
fun3 = @(x1,x2) 3*x1 + 3*x2 == 25;
fun4 = @(x1,x2) x1 + x2 == 16;
fplot(fun1)
hold on
fplot(fun2)
hold on
fplot(fun3)
hold on
fplot(fun4)

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Answer 1

Star Strider 2019-5-27

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/464251-plot-functions-and-intersections#answer_376799

在 MATLAB Online 中打开

The fsurf function takes two arguments:

figure
fsurf(fun1)
hold on
fsurf(fun2)
fsurf(fun3)
fsurf(fun4)
hold off

although you might find fcontour more applicable here:

func1 = @(x1,x2) 2*x1 + x2;
func2 = @(x1,x2) 3*x1 + 2*x2;
func3 = @(x1,x2) 3*x1 + 3*x2;
func4 = @(x1,x2) x1 + x2;
argrng = [-100 100  -100 100];
figure
fcontour(func1, argrng, 'LevelList',[1 1]*16)
hold on
fcontour(func2, argrng, 'LevelList',[1 1]*25)
fcontour(func3, argrng, 'LevelList',[1 1]*25)
fcontour(func4, argrng, 'LevelList',[1 1]*16)
hold off