Can someone tell me what I'm doing wrong. I have looked over this for quite a while already with no success. I think I am messing up when it comes to element by element operation, but I have tried everything I know with no luck.

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Frank_m 2015-4-3

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评论： Star Strider 2015-4-3

%this script will plot a 3-D plot of P(v) as a function of v and T
M=0.032;
R=8.31;
x=[0:1000];
y=[70:320];
[X,Y]=meshgrid(x,y);
Z=4*pi*(M/(Y.*2*pi*R)).^(3/2)*(X.^2).*exp((-X.^2*M)./(Y.*2*R))
surf(X,Y,Z)
xlabel('v (m/s)');ylabel('T (K)');zlabel('P(v)')

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Answer 1

Star Strider 2015-4-3

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When in doubt, vectorise everything!

This works:

M=0.032;
R=8.31;
x=[0:1000];
y=[70:320];
[X,Y]=meshgrid(x,y);
Z=4*pi*(M./(Y.*2*pi*R)).^(3/2).*(X.^2).*exp((-X.^2*M)./(Y.*2*R));
mesh(X,Y,Z)
xlabel('v (m/s)');ylabel('T (K)');zlabel('P(v)')

I replaced your surf call with mesh because the surf plot was so dense it looked completely black (in R2015a).

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John D'Errico 2015-4-3

编辑：John D'Errico 2015-4-3

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The black lines arise because matlab uses black edges in the grid. You can turn them off with a set command, something like

H = surf(X,Y,Z);
set(H,'edgecolor','none')

or you can use the shading command as I usually do, because it is easy to remember when I am feeling lazy.

surf(X,Y,Z)
shading interp

Either will kill the black lines in the surface.

Star Strider 2015-4-3

Thank you, John. I don’t myself encounter that problem often enough to have searched for a different solution other than switching to mesh. I’ll consider the 'edgecolor' and ‘shading’ options next time.

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