meshgrid plotting how to speficy x-axis and y-axis values?

I create a meshgrid and calculate a function camel. When I plot it, it displays indices, not X and Y values on the plot axes. How can I make it show the X and Y values on the plot axes instead?

[X,Y] = meshgrid(-3:0.1:3); camel = (4-2.1*X.^2+X.^4/3).*X.^2+X.*Y+4*(Y.^2-1).*Y.^2; imagesc(camel)

Answer 1

[Star Strider]

I’m not certain what you want to do.

Try this:

[X,Y] = meshgrid(-3:0.1:3);
camel = (4-2.1*X.^2+X.^4/3).*X.^2+X.*Y+4*(Y.^2-1).*Y.^2;  
figure(1)
surf(X,Y,camel)
grid on

[Jeff Eriksen]

when I use imagesc, contour, or surf to plot camel, the axes are labeled from 1-61 (indices). I want them labeled with the X and Y values from meshgrid, -3.0 through +3.0

[Star Strider]

I don’t understand your using those functions to plot it. If you want to restrict the axes to those limits and look at it from the top down, this works:

[X,Y] = meshgrid(-3:0.1:3);
camel = (4-2.1*X.^2+X.^4/3).*X.^2+X.*Y+4*(Y.^2-1).*Y.^2;  
figure(1)
surf(X,Y,camel)
grid on
axis tight
view([0, 90])

If you wnat it without the grid lines, this works:

[X,Y] = meshgrid(-3:0.1:3);
camel = (4-2.1*X.^2+X.^4/3).*X.^2+X.*Y+4*(Y.^2-1).*Y.^2;  
figure(1)
hs = surf(X,Y,camel);
grid on
axis tight
view([0, 90])
set(hs, 'LineStyle','none')

If you want a square plot, replace:

axis tight

with:

axis equal

[Jeff Eriksen]

Thanks for the additional info. I am more clear now on what each of these do now. I almost always use imagesc to plot a 2D matrix, whether it is correlations, a photograph, or just about anything. Very rarely do I wish to use surf. Now I realize surf works he way I want in this context since I pass it X and Y explicitly. For imagesc and contour, they rely on the indices and have no knowledge of the underlying (x,y) position of the matrix. So now my questions is refined as follows: how can I get imagesc and contour (the latter especially) to display the x,y position on the axes instead of the matric index numbers?

[Star Strider]

My pleasure.

The transition of my code to use contour (or here contourf) is straightforward:

[X,Y] = meshgrid(-3:0.1:3);
camel = (4-2.1*X.^2+X.^4/3).*X.^2+X.*Y+4*(Y.^2-1).*Y.^2;  
figure(1)
[C,hs] = contourf(X,Y,camel);
grid on
axis equal
view([0, 90])
set(hs, 'LineStyle','none')

To use imagesc requires a couple tweaks:

x = -3:0.1:3;
y = x;
figure(2)
imagesc(x,y,camel)
axis image

Experiment with the resolution of the meshgrid argument and ‘x’ (use the linspace function) to vary the resolution easily.