extrapolating data points/surface between two 3D lines

Hello all! I have two data sets (x,y,z1) (x,y,z2) where x, y and z are all seperate vectors of length n. I can plot each data set together as a 3D line plot using: plot3(x,y,z1,x,y,z2), but I would also like to interpolate/extrapolate the linear surface which exists between these two lines, effectively creating a 3D surface plot. Is there a good way to do this?

Answer 1

[Star Strider]

Without seeing your data, it’s difficult to be specific. See if griddata (or its friends) will do what you want.

[John]

The data is nothing special really, simply two 3D lines with equal number of points. for example

x  = [ 1 2 3 ];
y  = [ 1 2 3 ];
z1 = [ 4 4 5 ];
z2 = [ 1 2 8 ];

where line 1 is described by the points x,y,z1 and line 2 is described with the points x,y,z2. THe idea here is to create a surface between these lines.

[Star Strider]

The problem (that I didn’t appreciate before) is that (z1, z2) are defined at the same points. If you plot them using stem3, z1 are simply plotted on the same stems as z2.

If x and y are actually the same (as they are in your example), I suggest you use a 2D plot, such as the area plot to get the effect you want.

I suggest you experiment with patch for a 3D version of it. The patch function requires some experimentation to get it to do what you want.

Examples:

figure(1)
patch(x, y, [ z1; z2 ], 'g')
grid
view([15 30])

figure(2)
patch([0 x 0], [0 y 0], [0 z1 0; z1(1) z2 z2(3)], 'b')
grid on
view([15 30])