# Mesh for 3D plot

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K 2013 年 1 月 9 日
Hello, I have set of data x,y and z. When I plotted the data by using command 'plot3', there is no problem. However, when I tried to plot it by using command 'mesh', there is problem occured:
Z must be a matrix, not a scalar or vector
Can anyone help me to plot the surface of 3D plot?

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### 回答 (4 件)

Amith Kamath 2013 年 1 月 9 日

Going from the error, it seems that you are trying to use mesh for a 1D array (Z in your case). Mesh expects the 'Z' to be a 2D matrix containing all the values of the function, i.e. Z = f(x,y) as in the example from http://www.mathworks.com/help/matlab/ref/mesh.html :
figure;
[X,Y] = meshgrid(-8:.5:8);
R = sqrt(X.^2 + Y.^2) + eps;
Z = sin(R)./R;
mesh(Z);
So from http://www.mathworks.com/help/matlab/ref/plot3.html : plot3(X1,Y1,Z1,...), where X1, Y1, Z1 are vectors or matrices, plots one or more lines in three-dimensional space through the points whose coordinates are the elements of X1, Y1, and Z1.
whereas from http://www.mathworks.com/help/matlab/ref/mesh.html : mesh(X,Y,Z) draws a wireframe mesh with color determined by Z, so color is proportional to surface height. If X and Y are vectors, length(X) = n and length(Y) = m, where [m,n] = size(Z).
You got to make sure that size(Z) is [m,n]!
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Ryan Livingston 2013 年 1 月 9 日
A bit more detail would help in giving a precise answer. Including some example data or an example of a surface could assist folks in answering.
Generally for calling
mesh(x,y,z)
there are a few possibilities.
• x and y are vectors. Then, all of the pairs
(x(i), y(j)) for all i, j in range,
are taken to be your grid points. The value of the surface is then given by z(i,j) so that the points plotted are:
(x(i), y(j), z(i,j))
• x and y are matrices. Then the points plotted are:
(x(i,j), y(i,j), z(i,j))
In each case, the vertical values in "z" need to be a matrix with one value per grid point in order to provide the right number of values.
A little example:
x = linspace(-10,10,100);
y = linspace(-10,10,100);
z = repmat(x,[100 1]);
z = z.^2;
mesh(x,y,z);
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K 2013 年 1 月 9 日
The example of the data is like this:
DataA DataB DataC
0.06 0.14 0.5
0.07 0.15 0.5
0.08 0.19 0.5
0.06 0.13 1
0.08 0.15 1

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lala 2013 年 2 月 9 日
Hi. Please clarify more! i have the same problem! Thanks!
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lala 2013 年 2 月 9 日
Well, just a bit description: I have these points x, y, z points saying for example at x=2.5 and y=12, then z is 3:
x=[2.5 4 6 18 9]; y=[12 3 7.5 1 10]; z=[3 15 16 8 11.5];
and i want to create a 3D mesh.
lala-

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