Error: Z must be a matrix, not a scalar or vector

Question

Alexander Quinto 2017-12-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/372127-error-z-must-be-a-matrix-not-a-scalar-or-vector

评论： Walter Roberson 2017-12-10

Hey, so I am trying to plot this but I get this error. I'm fairly new to MATLAB so I dont know how to fix this issue. Thank you!

close all;
A1 = csvread('Circle6inch copy');
A2 = csvread('Circle12inchCopy');
A3 = csvread('Circle18inchCopy');
r = [6,12,18];
x = [cos(A1(:,1))*r(1); cos(A2(:,1))*r(2); cos(A3(:,1))*r(3)] ;
y = [sin(A1(:,1))*r(1); sin(A2(:,1))*r(2); sin(A3(:,1))*r(3)] ;
a = [A1(:,2); A2(:,2); A3(:,2)];
z = meshgrid(x,y);
n = length(x);
m = length(y);
for i = 1 : n
  for j = 1 : m
      z(i,j) = a(j);
  end 
end
[ii,ii] = unique(z','rows','first');
out = z(:,sort(ii));
z = out;
surf(x,y,a);

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Answer 1

jean claude 2017-12-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/372127-error-z-must-be-a-matrix-not-a-scalar-or-vector#answer_295545

read here you didn't use meshgrid in the right way

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Alexander Quinto 2017-12-10

在 MATLAB Online 中打开

Is this what I was doing wrong? When I try to plot this it gives me the error saying:

Error using matlab.graphics.chart.primitive.Surface/set Value must be a vector or 2D array of numeric type

Error in matlab.graphics.chart.internal.ctorHelper (line 8) set(obj, pvpairs{:});

Error in matlab.graphics.chart.primitive.Surface

Error in surf (line 150) hh = matlab.graphics.chart.primitive.Surface(allargs{:});

Error in datagraph (line 22) surf(X,Y,Z);

 close all;
A1 = csvread('Circle6inch copy');
A2 = csvread('Circle12inchCopy');
A3 = csvread('Circle18inchCopy');
r = [6,12,18];
x = [cos(A1(:,1))*r(1); cos(A2(:,1))*r(2); cos(A3(:,1))*r(3)] ;
y = [sin(A1(:,1))*r(1); sin(A2(:,1))*r(2); sin(A3(:,1))*r(3)] ;
a = [A1(:,2); A2(:,2); A3(:,2)];
n = length(x);
m = length(y);
for i = 1 : n
    for j = 1 : m
        z(i,j) = a(j);
    end 
end
[ii,ii] = unique(z','rows','first');
out = z(:,sort(ii));
z = out;
[X,Y,Z] = meshgrid(x,y,z);
surf(x,y,z);

Walter Roberson 2017-12-10

在 MATLAB Online 中打开

With three outputs, meshgrid() is going to output 3D arrays, but the z input to meshgrid needs to be 2D.

Aside from that, your code is dubious. Your lines

for i = 1 : n
    for j = 1 : m
        z(i,j) = a(j);
    end 
end

set all rows to have the same content. For example, z(1,5) = a(5), but also z(2,5) = a(5), z(3,5) = a(5) and so on. There does not appear to be much point in that.

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