3D the Grid

If we have a function of two variables , we need three axes to display the graph.

When plotting in 2D we use evenly spaced x-values and function values of these stored in a y-vector.

When plotting in 3D we need evenly spaced x- and y-values, spaced on a grid where each function value z is taken of a point (x, y) on the grid. In order to achieve this we use the command

meshgrid.

>>> x=linspace(-2,2,5)
x =

-2 -1 0 1 2

>>> y=linspace(-2,2,5)
y =

-2 -1 0 1 2

>>> [xx,yy]=meshgrid(x,y)
xx =

-2 -1 0 1 2
-2 -1 0 1 2
-2 -1 0 1 2
-2 -1 0 1 2
-2 -1 0 1 2

yy =

-2 -2 -2 -2 -2
-1 -1 -1 -1 -1
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2

Each point on the grid is made by taken an element from the xx-matrix as the x-value and the corresponding element from the yy-matrix as the y-value. All in all there are 25 points in this grid.