Create and combine quiver and contour plots

Im trying to figure out how to create and combine a quiver plot and a contourf using 4 vectors. I already have the quiver plot done but im stuck on the contourf. What i keep getting with the countourf is:

 Error using contourf (line 61)
 Z must be at least a 2x2 matrix.

 Error in Importingshit (line 9)
 contourf(x,y,vx,vy);

For the time being im just trying to get the contourf to work but if someone is willing to help me combine them then i would deffinitly not refuse. Thanks in advance!

[Thorsten]

Please post your data.

Answer 1

[Star Strider]

You’re calling contourf wrong. It doesn’t use the ‘vx’ and ‘vy’ (that I assume you use in your quiver plot). It wants a single square matrix ‘z’, or ‘x’, ‘y’, ‘z’ matrix arguments. See the documentation for it for details.

[Paul]

you are correct that i am using the vx and vy in my quiver but the question is, i have 6 vectors i am using but for these i only need 4 (x,y,vx,vy) but when i write contourf(x,y) it brings me an error also and when it did work it was wrong. How do i incorporate vx and vy into contour (or something similar) and then "overlay" it onto the quiver?

[Star Strider]

...‘but when i write contourf(x,y) it brings me an error also and when it did work it was wrong’...

1. What was the error it threw,
2. What was ‘wrong’ when it worked?

[Paul]

1.

 Error using contourf (line 61)
 Z must be at least a 2x2 matrix.

2. when it "worked" it was making a countour but the contours didnt match up with the quiver. They werent representing what they should have so i did something wrong.

[Star Strider]

What are the sizes of x and y?

What is the surface you want to plot? It has to be a matrix, and ideally a function of matrices X and Y. The surface Z must be some function of X and Y if you give it all three arguments.

We don’t have your data or code, so we’re purely guessing here.

Answer 2

[Thorsten]

 contourf(x,y,sqrt(vx.^2 + vy.^2));

[Paul]

same error as above:

 Error using contourf (line 61)
 Z must be at least a 2x2 matrix.