array to vector conversion

2011 4 15
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I have a 3-dimensional array A which has 450 rows,210 coulms, 4 layers. I want to make a regression between A(450,210,1) and A(450,210,3), A(450,210,2) and A(450,210,4). For that I need to convert the array to 4 vecotrs. I don't know how to do that. I tried Reshape function but couldn't get what I want. Any help is appericiated.

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Oleg Komarov
Oleg Komarov 2011-4-15

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A = rand(450,210,4);
EDIT
% Switch 2nd dim with 1st
A = permute(A,[2,1,3]);
% Reshape into vector each layer
A = reshape(A,450*210,4)
Each column now is the vectorized layer.

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Hassan
Hassan 2011-4-15
thanks a lot for the help. I think I need to do a step before using that since now it's writing the first column and then 2nd column, ... but I need first rwo,2nd row,...
A = rand(450,210,4);
A=tranpose(A(:,:,1))
A1 = reshape(A(:,:,1),450*210,1)
James Tursa
James Tursa 2011-4-15
You can use the MTIMESX FEX submission to do an nD transpose on your original A array. That will turn your rows into columns and get them next to each other in memory. Then you can do the rest of the calculation as shown above. e.g.,
A = mtimesx(1,A,'T'); % Transpose the first two dims
You can find MTIMESX here:
http://www.mathworks.com/matlabcentral/fileexchange/25977-mtimesx-fast-matrix-multiply-with-multi-dimensional-support
Hassan
Hassan 2011-4-17
thanks for the help. I couldn't run the code. it gives me an error which says A C/C++ compiler has not been selected with mex
-setup. I don't know what should I do to fix it.
Hassan
Hassan 2011-4-17
thanks Oleg for refining the code.
James Tursa
James Tursa 2011-4-17
Type the following at the MATLAB command line prompt:
mex -setup
Then press Enter
Then enter the number of a C compiler such as lcc
Then press Enter again
Then try running mtimesx again.
Hassan
Hassan 2011-4-22
thanks James, it's working now.

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