Index a v dimensional matrix from a matrix with v columns and n rows

Hello all,

I a have u row and n column matrix, say p, in which I want to store some data. I also have a matrix ind which has per each row the indices that I need in order to write to.

For example let me se the dimension to n=2 and supposing I want to write to position ind(1,:) of P I have:

ind = [1,2;2,6];
p(sub2ind([size(p,1),size(p,2)],ind(1,1),ind(1,1))) = datum; % Ican easly loop to handle more data

While this works I am not clear how to address the possibililty of having a 50 column (i.e. n=50) ind matrix as the prototype of subs2ind requires me to specify the indexes on by one.

Does anyone know how to deal with such scenario?

Answer 1

[madhan ravi]

 p(sub2ind(size(p), ind(:, 1), ind(:, 2)) = Dayum % where RHS should be equal to size(ind)

[Jpk]

I'm a bit confused as the code you highlight considers n=2 but not n=arbitrary number. You appear consider a generic u

The way I read it you are working on the rows, not the colums; I need a variable number of xolumns not of rows

Something like:

 p(sub2ind(size(p), ind(:, 1), ind(:, 2),ind(:, 3), .., ind(:,n)) = Dayum % where RHS should be equal to size(ind)

[madhan ravi]

You seems to understand what sub2ind() does. Please read the following doc more carefully:

 doc sub2ind

[Jpk]

You have to excuse me - I was not paying enough attention both in writing my question or in my reply. I will edit the question soon but allow me to reformulate.

Consider ind a t row and n column matrix of indices.

My goal is to use for each row of ind an index for a specific dimension of p. Of course n is know ahead of time.

eg.

ind = [1,2,4;2,6,5];
p( sub2ind(size(p),ind(1,1),ind(1,2),ind(1,3)) ) = datum; % in this case n=3

if n=4

ind = [1,2,4,5;2,6,5,9];
p( sub2ind(size(p),ind(1,1),ind(1,2),ind(1,3),ind(1,4)) ) = datum; % in this case n=4

In other words the kth colum of ind contains the indices for the kth dimension of p.

[madhan ravi]

 for k = 1 : size(ind, 1)
     I = num2cell(ind(k, :))
     p(sub2ind(size(p), I{ : }))= datum;
 end