How can I convert a cell to a matrix ?

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Anthony Cazin-Bourguignon
评论： Ameer Hamza 2020-11-4
Hello, I have a table that I would like to change into a matrix as below.
I tried "cell2matrix" but it doesn't work and I really don't know how to do it. It's for a job and I am very grateful to the person who will help me.
Thank you for your time
Anthony

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Stephen23
Stephen23 2020-11-4
编辑：Stephen23 2020-11-4
The simple and efficient approach:
X = reshape([output{:,1}],260,207);
y = reshape([output{:,2}],260,207);
Z = reshape([output{:,3}],260,207);
https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html
https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

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Ameer Hamza
Ameer Hamza 2020-11-4
编辑：Ameer Hamza 2020-11-4
If first matrix contains all combinations of row and columns in the order you mentioned,
C = [
1 1 1;
2 1 2;
3 1 3;
1 2 4;
2 2 5;
3 2 6;
1 3 7;
2 3 8;
3 3 9];
M = reshape(C(:,3), 3, 3)
For a general case, in which indexes in column 1 and 2 have an arbitrary order.
M = zeros(max(C(:,1)), max(C(:,2)));
idx = sub2ind(size(M), C(:,1), C(:,2));
M(idx) = C(:,3);
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Ameer Hamza
Ameer Hamza 2020-11-4
Ok, I get it now. scatteredInterpolant seems suitable here:
x = unique([output{:,1}]);
y = unique([output{:,2}]);
[Xg, Yg] = ndgrid(x, y);
mdl = scatteredInterpolant([output{:,1}].', [output{:,2}].', [output{:,3}].');
M = mdl(Xg, Yg);
To see the relation between value of x, y and data column, run the following code
T = array2table(M, 'VariableNames', string(y));
T.Row = string(x);

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Rik
Rik 2020-11-4
You need to use accumarray to create this. You can find examples in the documentation for that function:
doc accumarray
  2 个评论
Anthony Cazin-Bourguignon
Anthony Cazin-Bourguignon 2020-11-4
Hello Rik, I've read the documentation but I don't really see how this could solve my problem. Would it be possible for you to show me a small example with the values of the photo I put in the question? I'm still a beginner in matlab
Thank you
Rik
Rik 2020-11-4
Your example only contained integer indices, while the picture of your actual data contains decimal values. You need to make sure you have a set of integer values, which you could do with unique:
x=[-3.53;-3.53;-4.53;-4.53];
y=[51.05;51.10;51.05;51.10];
z=rand(size(x));
[x_unique,~,x_int]=unique(x);
[y_unique,~,y_int]=unique(y);
subs=[x_int y_int];
data=accumarray(subs,z);

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Steven Lord
Steven Lord 2020-11-4
What specific type of variable are you using to store your data? If it's in a table array take a look at the unstack function. The first example on that documentation page looks very similar to your picture.
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Anthony Cazin-Bourguignon
Anthony Cazin-Bourguignon 2020-11-4
Hi, my data are stored in a cell of 53820x3 and I need to make a matrix of 260x207 with it. I dont know if it's work with unstack function

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