Scatte plot to contour plot xyz data.

Hi I have a matrix called Total that is 3x100, the first column is the x value, the second column is the y value and the last column is the z value. When I input this matrix into a scatter plot I get a scatterplot with 3 paralell lines which is correct as I am mapping metal beams underneath concreate and the z value is the electrmagnetic value of the bar, how can I turn this graph into a contourf plot or a color plot.

Thanks

Answer 1

[Star Strider]

Several MATLAB plot types require the ‘Z’ argument to be a matrix.

One way of creating it is to interpolate it, and one way of doing that is this example where ‘x’, ‘y’ and ‘z’ are the original vectors:

N = 50;                                                 % Number Of Points Desired
xv = linspace(min(x), max(x), N);
yv = linspace(min(y), max(y), N);
[X,Y] = ndgrid(xv, yv);
Z = griddata(x, y, z, X, Y);

figure
contourf(X, Y, Z)
axis('equal')

Experiment with it with your data.

Answer 2

[Christopher McCausland]

Hi,

Have you tried Contour3 for three dimentional contour plots? You should be able to plot a secondary graph from this.

contour3(X,Y,Z);

Kind regards,

Christopher

[Quinn Coughlin]

Hi Christopher

Thanks for getting back to me, I am trying to get a 2d graph of the data. Also I get a error saying that Z needs to be a 2x2 matrix, how can I fix this?

Thanks Quinn

[Christopher McCausland]

@Quinn Coughlin My appologies, I misunderstood what you were asking for. @Star Strider has a very good description below! Another way to interpolate is with cubic splines which would be a little smoother however I would say its probably overkill for this.