How to plot values of a variable Z on an arbitrary 2D path in X and Y

Hello,

What I would like to do is basically to plot values of a matrix Z along a path defined by points {(X1,Y1); (X2,Y2)} inside its domain.

if we take as an example this code from the meshgrid command examples:

x = -2:0.25:2;
y = x;
[X,Y] = meshgrid(x);
F = X.*exp(-X.^2-Y.^2);
surf(X,Y,F)

What I would like to do is to make a 2D plot of the values of Z along a straight path line defined by two points. the next picture gives an idea of the path seen from the top.

In my case the values of Z are not calculated from an explicit formula but are numerical results forma nother code, and they have been interpolated using the function griddata, since I only had vectors before.

Thank you for the help!

Answer 1

[Cris LaPierre]

Since you have the equation, just create vertors for X and Y of the line, then solve for Z using those values.

Assuming that's not necessarily the case all the time, you could also use interp2 to interpolate the values of Z along the line using the known gridded data, as well as the X and Y values of the line.

x = -2:0.25:2;
y = x;
[X,Y] = meshgrid(x);
F = X.*exp(-X.^2-Y.^2);
surf(X,Y,F)
view(2)

% Define an arbitrary straight-line path
hold on
plot3([-1.5 -0.1],[1.75 -1.7],[1 1],'r-o','LineWidth',3)
hold off

% Use interp2 with X and Y vectors of the line to solve for z
xq=linspace(-1.5,-0.1,15);
yq=linspace(1.75,-1.7,15);
vq=interp2(X,Y,F,xq,yq);

figure
plot(vq)

[Gianluca Vernassa]

Ok great thank you! That was blind fast! I'm astonished.

Interp2 is doing the job perfectly, and indeed in my case I had numerical data coming from a finite element code, so there was no direct formula. My apologies if it wasn't clear.

Thank you very much.

Gianluca