Question

I am trying to create a 3D plot in Matlab.

I have a very long problem starting with the data set of Y and Z. With much manipulation it boils down to a simple y/z problem

y=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
z=[5, 10, 15, 20, 25, 30, 35, 40, 45, 50];


x=(y_new)/(z_new)

There is about 100 lines of equations manipulating y and z, to become two new variables y_new and z_new. I would like to create a 3d plot of x,y,z. I would want an x value for (1,5) and (1,10), (2,5), (2,10) etc.

The way I have the problem setup is only using y=1 and z=5. I have been trying to use for-loops or while-loops for the past few hours but I am getting stuck.

If someone can help me I would appreciate the time and effort!

Answer 1

You don’t need to use a for loop. Instead, use the builtin function meshgrid() which is designed to solve exactly this problem.

Here’s a tutorial from ‘abbe’ at MIT which details how to create a 3D plot of a function f(x,y) using meshgrid().

To quote the blurb:

3D plotting

When you make a 3-dimensional plot, you usually have a z variable that
is a function of both x and y. When you want x and y to vary over some
range, you need a matrix (rather than a vector) for x and y to get a
complete domain that covers all the different combinations of those x
and y values over some range. A function called meshgrid will set up x
and y matrixes like this for you. The x matrix varies the x down rows
and keeps it constant in columns, and the y matrix varies the y in
columns and keeps it constant across rows, so you get all combinations
of x and y if you use the two matrices.