Description of sltensor_unfold

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sltensor_unfold

PURPOSE

SLTENSOR_UNFOLD Unfolds a tensor to a matrix

SYNOPSIS

function M = sltensor_unfold(T, k)

DESCRIPTION

SLTENSOR_UNFOLD Unfolds a tensor to a matrix 

 $ Syntax $
   - M = sltensor_unfold(T, k)

 $ Arguments $
   - T:        the tensor
   - k:        the dimension along which the tensor is unfolded
   - M:        the matrix obtained by unfolding the tensor

 $ Description $
   - M = sltensor_unfold(T, k) Unfolds a tensor T to the matrix M along
   the k-th dimension.

 $ History $
   - Created by Dahua Lin on Dec 17th, 2005

CROSS-REFERENCE INFORMATION

This function calls:

• raise_lackinput RAISE_LACKINPUT Raises an error indicating lack of input argument

This function is called by:

• sltensor_multiply SLTENSOR_MULTIPLY Multiplies a tensor and a matrix
• sltensor_svd SLTENSOR_SVD Performs a Higher-Order SVD on a Tensor

SOURCE CODE

0001 function M = sltensor_unfold(T, k)
0002 %SLTENSOR_UNFOLD Unfolds a tensor to a matrix
0003 %
0004 % $ Syntax $
0005 %   - M = sltensor_unfold(T, k)
0006 %
0007 % $ Arguments $
0008 %   - T:        the tensor
0009 %   - k:        the dimension along which the tensor is unfolded
0010 %   - M:        the matrix obtained by unfolding the tensor
0011 %
0012 % $ Description $
0013 %   - M = sltensor_unfold(T, k) Unfolds a tensor T to the matrix M along
0014 %   the k-th dimension.
0015 %
0016 % $ History $
0017 %   - Created by Dahua Lin on Dec 17th, 2005
0018 %
0019 
0020 %% parse and verify
0021 if nargin < 2
0022     raise_lackinput('sltensor_unfold', 2);
0023 end
0024 
0025 %% compute
0026 n = ndims(T);
0027 if k == 1
0028     M = T(1:end, :);
0029 elseif k <= n
0030     if k < n
0031         pdims = [k, 1:k-1, k+1:n];
0032     else
0033         pdims = [k, 1:k-1];
0034     end
0035     M = permute(T, pdims);
0036     M = M(1:end, :);
0037 else
0038     M = T(:)';
0039 end
0040 
0041 
0042 
0043 
0044 
0045 
0046     
0047

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