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From: Kevin Kleine on 16 Apr 2010 11:44
Does anyone know how I can use a vector V, for instance V = [3 2], as an index for a multidimensional array M = [ 1 2 3 ; 4 5 6 ; 7 8 9 ], so that M(function(V)) = 8 ????
From: Matt Fig on 16 Apr 2010 11:55
Have a look at SUB2IND.
From: Yi Cao on 16 Apr 2010 11:57
"Kevin Kleine" <kikleine(a)gmail.com> wrote in message <hqa0k5$i5c$1(a)fred.mathworks.com>...
> Does anyone know how I can use a vector V, for instance V = [3 2], as an index for a multidimensional array M = [ 1 2 3 ; 4 5 6 ; 7 8 9 ], so that M(function(V)) = 8 ????

One way to do it is convert the vector V to a linear index,

n = size(M,1);
f = V(1) + (V(2)-1)*n;
M(f) %should be 8

HTH
Yi
From: Kevin Kleine on 16 Apr 2010 13:20
thanks for the quick reply, however:

I don't know in advance the size or number of dimensions of the matrix. It might just as well be a 6-dimensional matrix. To use sub2ind, or your method, the matrix has to have a fixed size, or am I mistaken?
From: Matt Fig on 16 Apr 2010 13:44
SUB2ind takes the size of the array as an input argument. If V may have the same number of elements as M has dimensions, use comma-separated list syntax by using NUM2CELL on V. For example:

% Randomly dimensioned data
M = rand(cellfun(@(x) ceil(rand*2)+4,cell(1,ceil(rand*8))));
V = ceil(rand(1,ndims(M))*3)

% Index into M.
Vc = num2cell(V)
M(sub2ind(size(M),Vc{:}))
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