MATLAB: 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.

plotssurf

%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)')

Best Answer

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).

Related Solutions

MATLAB: 3d plot error

You were missing some multiplication operators in your functions. (MATLAB does not recognise implicit multiplication.) I also created your functions as anonymous functions (see Function Basics (link) for details), and then did the plots. The Symbolic Math Toolbox is not always the best option unless you want to specifically do symbolic calculations. Here, it is not necessary.

The Code:

f1 = @(x,y,z) 8*x.^3+36*y.^3+z.^2-36;
f2 = @(x,y,z) 4*x.^2-y.^2-21*z;
f3 = @(x,y,z) 4*x.^2-2*y.^2+10*z.^2;
xxx = linspace(-3,3);
yyy = linspace (-3,3);
[x,y] = meshgrid(xxx,yyy);
z = 1;
figure(1)
mesh(x,y,f1(x,y,z))
hold on
mesh(x,y,f2(x,y,z))
mesh(x,y,f3(x,y,z))
hold off
grid on

MATLAB: This code crashes the MATLAB and I don’t know y figure(2); x = linspace(0,2); y = linspace(5,7); [X,Y]=meshgrid(x,y); Z = sin(XY).Y + Yexp(-cos(XY^2)).*X; mesh(X,Y,Z); xlabel(‘x’); ylabel(‘y’); zlabel(‘z’); grid on; title(‘Question 4 plot’);

Z = sin(X*Y).*Y + Y*exp(-cos(X*Y^2)).*X;

I guess you want:

Z = sin(X .* Y) .* Y + Y .* exp(-cos(X .* Y^2)) .* X;

Note: Whenever you mention a "crash", post the complete error message.

Best Answer

Related Solutions

MATLAB: 3d plot error

MATLAB: This code crashes the MATLAB and I don’t know y figure(2); x = linspace(0,2); y = linspace(5,7); [X,Y]=meshgrid(x,y); Z = sin(X*Y).*Y + Y*exp(-cos(X*Y^2)).*X; mesh(X,Y,Z); xlabel(‘x’); ylabel(‘y’); zlabel(‘z’); grid on; title(‘Question 4 plot’);

Related Question

MATLAB: This code crashes the MATLAB and I don’t know y figure(2); x = linspace(0,2); y = linspace(5,7); [X,Y]=meshgrid(x,y); Z = sin(XY).Y + Yexp(-cos(XY^2)).*X; mesh(X,Y,Z); xlabel(‘x’); ylabel(‘y’); zlabel(‘z’); grid on; title(‘Question 4 plot’);