I have a matrix that looks like the following.
I want to take the column 3 values and put them in another matrix, according to the following rule.
The value in the Column 5 is the row index for the new matrix, and Column 6 is the column index. Therefore 20 (taken from 29,3) should be in Row 1 Column 57 of the new matrix, 30 (from 30,3) should in Row 1 column 4 of the new matrix, and so on.
If the value in column 3 is NaN then I want NaN to be copied over to the new matrix.
Example:
% matrix of values and row/column subscripts
A = [
20 1 57
30 1 4
25 1 16
nan 1 26
nan 1 28
25 1 36
nan 1 53
50 1 56
nan 2 1
nan 2 2
nan 2 3
80 2 5
];
% fill new matrix
B = zeros(5,60);
idx = sub2ind(size(B), A(:,2), A(:,3));
B(idx) = A(:,1);
There are a couple other ways to do this, but I think the above code is easy to understand. It is using linear indexing.
Assuming you don't have duplicate subscripts, you could also use:
B = full(sparse(A(:,2), A(:,3), A(:,1), m, n));
(where m and n are the output matrix size)
Another one:
B = accumarray(A(:,[2 3]), A(:,1), [m,n]);
x = rand(1,10); x(1.3) (ERROR!)I am not sure if I understood your question clearly but this might help:
(Assuming your main matrix is A)
nRows = max(A(:,5));
nColumns = max(A(:,6));
FinalMatrix = zeros(nRows,nColumns);
for i=1:size(A,1)
FinalMatrix(A(i,5),A(i,6))=A(i,3);
end
Note that above code sets the rest of the elements equal to zero.
sub2indin the documentation