Question

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How do I make a surf plot in MATLAB with irregularly spaced data?

I have such data:

data = [
x1 y1 z1
x2 y2 z2
...
xn yn zn
];

I need to get surface of this data. Third row, z – will be the height of surface. But Xs and Ys are not monotonic continous data, so this doesn’t work:

[X Y] = meshgrid(data(:,1), data(:,2));
Z = interp2(data(:,1), data(:,2), data(:,3), X, Y);

because my data in first and second row is not monotonic.

Update:

TriScatteredInterp can do this.(Thanks @Rody Oldenhuis)

F = TriScatteredInterp(data(:,1), data(:,2), data(:,3))
ti=1:10:600;
[qx qy] = meshgrid(ti, ti);
qz = F(qx, qy);
mesh(qx, qy, qz);

Answer 1

I think you’re looking for TriScatteredInterp. From the documentation:

F = TriScatteredInterp(X, V) creates an interpolant that fits a
surface of the form V = F(X) to the scattered data in (X, V). X is a
matrix of size mpts-by-ndim, where mpts is the number of points and
ndim is the dimension of the space where the points reside (ndim is 2
or 3). The column vector V defines the values at X, where the length
of V equals mpts.

F = TriScatteredInterp(X, Y, V) and F = TriScatteredInterp(X, Y, Z, V)
allow the data point locations to be specified in alternative column
vector format when working in 2-D and 3-D.