Convert x y coordinates and z data to Matrix

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user20912 2022-9-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1806060-convert-x-y-coordinates-and-z-data-to-matrix

回答： Robert Daly 2023-8-11

采纳的回答： Star Strider

在 MATLAB Online 中打开

I have three vectors

>> whos x y VAR1
  Name          Size             Bytes  Class     Attributes
  x          21242x1             679744  double              
  y          21242x1             679744  double              
  var1       21242x1             679744  double              

where X and Y represent the location of the corresponding value of var1. What Im trying to do is to convert all this data to a matrix.

What I've done until now is:

a1 = 21242;
m = zeros(a1,a1).*NaN;
indexes = sub2ind([a1,a1],x,y);
m(indexes) = var1

Based on this question but I'm getting an error

Error using sub2ind (line 43)
Out of range subscript.

Which, according to another question about this error, is because I'm trying access elements which does not exist on the matrix.

Any help?

Thanks!

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user20912 2022-9-15

在 MATLAB Online 中打开

Thank for the input. However, it's still not working.

I have tried to element by element with a for cycle:

for i1=1:a1
    indexes = sub2ind([a1 a1], abs(x(i1)), y(i1));
    i1
end

and the problem is in the element 3897:

>> x(3896:3898)
   -1.0021
   -0.9993
   -1.0026
   

what's the problem with that numbers? I can not find the reason why keep failing.

Dyuman Joshi 2022-9-15

Indices should also be integers as well.

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采纳的回答

Star Strider 2022-9-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1806060-convert-x-y-coordinates-and-z-data-to-matrix#answer_1054280

It would help to have the actual vectors.

It may be possible to use the reshape function to create matrices from the vectors, if the vectors are from a gridded original matrix. The easiest way to determine the dimensions of the arrays is to use the unique function and look at the second output. The elements of the second output should be regularly-spaced, and that difference is one dimension to specify in the reshape call, with the other one left as the empty vector [].

Otherwise, use linspace, ndgrid and griddata to create appropriate matrices from scattered data.