Beginner: Using SURF Function, Error: Z must be a matrix, not a scalar or vector.
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Hi,
I've never used the surf function before and I am getting this error that I do not understand. I've read the other posts on this and still can't figure out what I need to do.
My situation:
xA is 5001 x 1 double
yA is 5001 x 1 double
zA is 5001 x 1 double
What can't I just do [x,y] = meshgrid(xA,yA) then surf(x,y,zA)? I don't see what other info the function would need to make a surface. Can someone tell me how to get this working?
采纳的回答
Walter Roberson
2020-8-11
N = 250;
xvec = linspace(min(xA), max(xA), N);
yvec = linspace(min(yA), max(yA), N);
[X, Y] = ndgrid(xvec, yvec);
F = scatteredInterpolant(xA, yA, zA);
Z = F(X, Y);
surf(X, Y, Z, 'edgecolor', 'none');
更多回答（1 个）
Cris LaPierre
2020-8-11
1 个投票
A surface is a 3D plot. All your X values are repeated for every Y value, and vice versa, meaning the surface is 5001 x 5001. Surf automatically can handle a vector for X and Y, but Z must be the matrix containing the Z value for every combination of X and Y.
Typically, you use meshgrid to create X and Y, then use those matrices to compute the values of Z.
Where you already have all 3, you likely need to reshape them to form matrices.
3 个评论
Walter Roberson
2020-8-11
If you have a vector of X, Y, Z, then you have a 3D line, not a surface, unless you interpolate.
James Parkus
2020-8-11
Cris LaPierre
2020-8-12
编辑：Cris LaPierre
2020-8-12
@Walter: That's why I said to use scatter3. This allows you to view the data first to see if it even could create a surface, or if it is just a line. It is possible to record all the points for a surface in a vector. If the result does end up looking like it could be a surface, then you might be able to just reshape the vectors into matrices that can be plotted using surf.
Here's a simple example so I don't completely lose James.
xA = [-1 -1 -1 -1 0 0 0 0 1 1 1 1];
yA = [-1 0 1 2 -1 0 1 2 -1 0 1 2];
zA = [2 1 2 5 1 0 1 4 2 1 2 5];
xB = reshape(xA,[4,3]);
yB = reshape(yA,[4,3]);
zB = reshape(zA,[4,3]);
figure
surf(xB,yB,zB)
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