Plotting Multiple Curves on the Same Graph

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Hollis Williams 2019-7-16

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https://ww2.mathworks.cn/matlabcentral/answers/471936-plotting-multiple-curves-on-the-same-graph

评论： Star Strider 2019-7-18

I am plotting a graph of radial velocity against varying radius, but there is also a parameter in the velocity expression similar to the Reynolds number which can have various values, so I would like to set the value of the parameter to 0, 1 and 0.2 and to plot three curves on the same graph, what would be the easiest way to do this?

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Adam 2019-7-16

在 MATLAB Online 中打开

doc hold

Set e.g.

hold( hAxes, 'on' )

for your axes with handle hAxes, then you can add as many plots as you like.

Alternatively if you have all the results together in a matrix (assuming they are the same length for each parameter) you can just plot the matrix all in one go using

doc plot

and making sure you have it oriented the right way.

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Star Strider 2019-7-16

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It depends on your function and what you want to do:

t = linspace(0, 2*pi);
freq = [1 5 9];
ampl = [1 2 3];
s = bsxfun(@times, ampl(:), sin(freq(:)*t));
figure
plot(t, s)
grid

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Hollis Williams 2019-7-18

Many thanks for your answer, I have tried something slightly different but getting a bit of an unexpected error message. So now I am trying:

bt = @(Kn) -sqrt(pi/2)*(30*Kn.^2 + 180*(1+(1./pi))*Kn.^3)./(20*pi + 135*pi*Kn + 9*(25*pi +18)*Kn.^2 +324*Kn.^3);

theta = @(R,Kn) (bt./(R.^2));

Knv = [0, 0.2, 1];

Rv = 1:10;

[Rm,Knm] = meshgrid(Rv,Knv);

figure

plot(Rv, theta(Rm,Knm))

grid

%xlabel('R')

lgdc = sprintfc('K_n = %3.1f', Knv);

legend(lgdc, 'Location','SE')

I seem to get an error message related saying that the ./ in the expression for theta is an undefined operator for input arguments of type 'function_handle', although I have used it elsewhere with no problems.

Star Strider 2019-7-18

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As always, my pleasure!

Remember that in my code, ‘bt’ is a function, so it needs to be evaluated in any calculation using it, and that requires that it be supplied with a numeric argument so that it can return a numeric result:

theta = @(R,Kn) (bt(Kn)./(R.^2));

The complete code is now:

bt = @(Kn) -sqrt(pi/2)*(30*Kn.^2 + 180*(1+(1./pi))*Kn.^3)./(20*pi + 135*pi*Kn + 9*(25*pi +18)*Kn.^2 +324*Kn.^3);
theta = @(R,Kn) (bt(Kn)./(R.^2));
Knv = [0, 0.2, 1];
Rv = 1:10;
[Rm,Knm] = meshgrid(Rv,Knv);
figure
plot(Rv, theta(Rm,Knm))
grid
%xlabel('R')
lgdc = sprintfc('K_n = %3.1f', Knv);
legend(lgdc, 'Location','SE')