MATLAB: Error using ==> mesh at 80 Z must be a matrix, not a scalar or vector.

3d ploterror

Hi, I'm trying to plot this code, but I'm not sure what went wrong.

 x=0:1:40;
y=0:1:40;
[X,Y]=meshgrid(x,y);
a=0.5;
b=0.5;
k=length(x);
gt=0.5;
o=20;
for v=1:1:k
    if X(v)==0||Y(v)==0
       Z(v)=(a.^2)*sqrt(exp(-o)*(o.^(X(v)+1))./factorial(X(v)+1))*sqrt(exp(-o)*(o.^(Y(v)+1))./factorial(Y(v)+1))*cos(gt*sqrt(X(v)+1))*cos(gt*sqrt(Y(v)+1))+(b.^2)*sqrt(exp(-o)*(o.^X(v))./factorial(X(v)))*sqrt(exp(-o)*(o.^Y(v))./factorial(Y(v)))*cos(gt*sqrt(X(v)))*cos(gt*sqrt(Y(v)));
    else
       Z(v)=2;
    end
end
mesh(X,Y,Z)
xlabel('n');ylabel('m')
zlabel('P')

Best Answer

You are only iterating over the first column of X. You are using linear indexing into a 2D array, and you are only going as far as length(x) when the 2D array is length(x) by length(y).

I suggest that you do not loop at all. I suggest that you completely vectorize the construction of your Z in terms of X and Y, under the assumption that neither X nor Y is 0. And then use logical indexing to assign the 2 to the locations in Z corresponding to X or Y being 0.

Related Solutions

MATLAB: Can someone help me with these 3D plots

you can plot these shapes in the following two ways(you can choose better way you like):

%%Seashell

[u, v] = meshgrid(linspace(0, 6 * pi, 100), linspace(0, 2 * pi, 100));
x = 2 * (1 - exp(u / (6 * pi))) .* cos(u) .* (cos(0.5 * v))^2;
y = 2 * (-1 + exp(u / (6 * pi))) .* sin(u) .* (cos(0.5 * v))^2;
z = 1 - exp(u / (3 * pi)) - sin(v) + exp(u / (6 * pi)) .* sin(v);
figure, surf(x, y, z), xlabel('x'), ylabel('y'), zlabel('z'), title('Seashell')
%%Eight torus

c = 1;
[u, v] = meshgrid(linspace(-pi, pi, 100));
x = cos(u) .* (c + sin(v) .* cos(u) - sin(2 * v) .* (sin(u) / 2));
y = sin(u) .* (c + sin(v) .* cos(u) - sin(2 * v) .* (sin(u) / 2));
z = sin(u) .* sin(v) + cos(u) .* (sin(2 * v) / 2);
figure, surf(x, y, z), xlabel('x'), ylabel('y'), zlabel('z'), title('Eight torus')
%%Helical spring

r1 = 0.25;
r2 = 0.25;
T = 2;
n = 6;
[u, v] = meshgrid(linspace(0, 2 * n * pi, 100), linspace(0, 2 * pi, 100));
x = (1 - r1 * cos(v)) .* cos(u);
y = (1 - r1 * cos(v)) .* sin(u);
z = r2 * (sin(v) + T * u / pi);
figure, surf(x, y, z), xlabel('x'), ylabel('y'), zlabel('z'), title('Helical spring')
%%Cornucopia

a = 0.3;
b = 0.5;
[u, v] = meshgrid(linspace(0, 2 * pi, 100), linspace(-3, 3, 100));
x = exp(b * v) .* cos(v) + exp(a * v) .* cos(u) .* cos(v);
y = exp(b * v) .* sin(v) + exp(a * v) .* cos(u) .* sin(v);
z = exp(a * v) .* sin(u);
figure, surf(x, y, z), xlabel('x'), ylabel('y'), zlabel('z'), title('Cornucopia')

Or alternatively you can also plot them using ezsurf as follows:

syms u v
%%Seashell
x = 2 * (1 - exp(u / (6 * pi))) * cos(u) * (cos(0.5 * v))^2;
y = 2 * (-1 + exp(u / (6 * pi))) * sin(u) * (cos(0.5 * v))^2;
z = 1 - exp(u / (3 * pi)) - sin(v) + exp(u / (6 * pi)) * sin(v);
figure, ezsurf(x, y, z)
%%Eight torus
c = 1;
x = cos(u) * (c + sin(v) * cos(u) - sin(2 * v) * (sin(u) / 2));
y = sin(u) * (c + sin(v) * cos(u) - sin(2 * v) * (sin(u) / 2));
z = sin(u) * sin(v) + cos(u) * (sin(2 * v) / 2);
figure, ezsurf(x, y, z)
%%Helical spring
r1 = 0.25;
r2 = 0.25;
T = 2;
n = 6;
x = (1 - r1 * cos(v)) .* cos(u);
y = (1 - r1 * cos(v)) .* sin(u);
z = r2 * (sin(v) + T * u / pi);
figure, ezsurf(x, y, z)
%%Cornucopia
a = 0.3;
b =0.5;
x = exp(b * v) .* cos(v) + exp(a * v) .* cos(u) .* cos(v);
y = exp(b * v) .* sin(v) + exp(a * v) .* cos(u) .* sin(v);
z = exp(a * v) .* sin(u);
figure, ezsurf(x, y, z)

I hope it helps. Good luck!

MATLAB: Undefined variable “cos” or class “cos”. Error in P4Afara_Question2 (line 5) z = (cos(x)).cos(sqrt(x.^2 + y.^2)).exp(-1abs(0.2*x));

 z = (cos(x)) .* cos(sqrt(x.^2 + y.^2)) .* exp(-1*abs(0.2*x));

Best Answer

Related Solutions

MATLAB: Can someone help me with these 3D plots

MATLAB: Undefined variable “cos” or class “cos”. Error in P4Afara_Question2 (line 5) z = (cos(x)).*cos(sqrt(x.^2 + y.^2)).exp​(-1*abs(0.​2*x));

Related Question

MATLAB: Undefined variable “cos” or class “cos”. Error in P4Afara_Question2 (line 5) z = (cos(x)).cos(sqrt(x.^2 + y.^2)).exp(-1abs(0.2*x));