convert plot3 to contour plot

Hi,

I have a novice question in matlab.

Say that I have some matrix

a = [1 2 3; 4 5 6; 7 8 10; 11 12 13]

I can plot this in 3d where column 1 is the x-axis, column 2 is the y-axis, and column 3 is the z-axis, by writing

plot3(a(:,1),a(:,2),a(:,3),'.').

However, I also want to make a contour plot where I have column 1 along the x-axis, column 2 along the y-axis, and column 3 represents the heights above the z = 0 plane. To do this I have to reshape my data somehow so that I can write something like

contourf(X,Y,Z).

How can I do this efficiently?

Answer 1

[Star Strider]

Use the griddata function:

a = randi(9, 10, 3);
x = a(:,1);
y = a(:,2);
z = a(:,3);

xv = linspace(min(x), max(x),  6);
yv = linspace(min(y), max(y),  8);

[X,Y] = meshgrid(xv, yv);
Z = griddata(x,y,z,X,Y);

figure
contourf(X, Y, Z)
colorbar

The griddata function had problems with your original ‘a’ matrix, so I created one it would work with.