How can I convert a cell to a matrix ?

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

Answer 1

[Stephen23]

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

Answer 2

[Ameer Hamza]

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);

[Anthony Cazin-Bourguignon]

Hello Ameer,

I have to change a table to get a matrix. In this table, I have 2 columns with values for X and for Y and a column on the right (the one with the X1, X2... X9) with the results of the calculations with x and y as input. I want to create a 3x3 matrix with the right result, M(1,1)=X1; M(3,3)=X9

[Ameer Hamza]

Yes, the code in my answer does that. Do you want something different?

[Anthony Cazin-Bourguignon]

Ah, maybe I don't understand the code well then.

The table I would like to reorganize is the one on the picture below. It is 53820x3. With your code above,

how could I rearrange my table?

Thank you for your time

[Anthony Cazin-Bourguignon]

Ah and my output matrix should be 260x207

[Ameer Hamza]

The X and Y values are not integers. Can you share the data in a .mat file?

[Anthony Cazin-Bourguignon]

Here u go

[Ameer Hamza]

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);

Answer 3

[Rik]

You need to use accumarray to create this. You can find examples in the documentation for that function:

doc accumarray

[Anthony Cazin-Bourguignon]

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]

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);

Answer 4

[Steven Lord]

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.

[Anthony Cazin-Bourguignon]

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