Making a 2D plot of an equation against 2 datasets

Hello,

I am trying to make a 2D plot of x and y based on a certain relation between them

Let:

x= 1:1:20

y= 1:0.5:8

Now, I want to plot z= x*y against x and y in the xy plane. Also, I only want to see the values of z such that z <10 or any other range .

Can someone please tell me how to do this? It seems simple, but I’m not a MATLAB Wiz.

Regards,

Answer 1

[jonas]

x = 1:1:20;
y = 1:0.5:8;

[X,Y] = meshgrid(x,y);
Z = X.*Y;
surf(X,Y,Z)
zlim([0 10]);

You could also replace the last two lines by something like

scatter3(X(Z<10),Y(Z<10),Z(Z<10),[],Z(Z<10))

[Kyle]

Thank you sir. But this is a 3D plot. I want it in 2D. Regards,

[jonas]

Like this?

scatter(X(Z<10),Y(Z<10),[],Z(Z<10))

or

Z(Z>=10)=NaN;
imagesc(X(:),Y(:),Z)

or

Z(Z>=10)=NaN;
contourf(X,Y,Z)

Answer 2

[Star Strider]

For a 2D version, try this:

x = 1:1:20;
y = 1:0.5:8;
z = bsxfun(@times, x, y');
z(z >= 10) = NaN;

figure
plot(z)
grid

Using contour with specific labeled levels:

x = 1:1:20;
y = 1:0.5:8;
[X,Y] = ndgrid(x,y);
Z = X.*Y;

figure
[C,h] = contour(X, Y, Z, 1:0.5:10);
Lvls = h.LevelList;
h.LevelList = Lvls(Lvls < 10);
clabel(C, h, Lvls(1:2:end))
xlabel('X')
ylabel('Y')