Description of sltensor_fold

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sltensor_fold

PURPOSE

SLTENSOR_FOLD Folds a matrix into a tensor

SYNOPSIS

function T = sltensor_fold(M, dims, k)

DESCRIPTION

SLTENSOR_FOLD Folds a matrix into a tensor

 $ Syntax $
   - T = sltensor_fold(M, dims, k)

 $ Arguments $
   - M:                the unfolded matrix of the tensor
   - dims:             the dimension sizes of the tensor
   - k:                the dimension along which the tensor is folded
   - T:                the resultant tensor

 $ Description $
   - T = sltensor_fold(M, dims, k) folds the matrix M to a tensor with
   its mode dimensions specified in dims along the k-th mode.

 $ 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

SOURCE CODE

0001 function T = sltensor_fold(M, dims, k)
0002 %SLTENSOR_FOLD Folds a matrix into a tensor
0003 %
0004 % $ Syntax $
0005 %   - T = sltensor_fold(M, dims, k)
0006 %
0007 % $ Arguments $
0008 %   - M:                the unfolded matrix of the tensor
0009 %   - dims:             the dimension sizes of the tensor
0010 %   - k:                the dimension along which the tensor is folded
0011 %   - T:                the resultant tensor
0012 %
0013 % $ Description $
0014 %   - T = sltensor_fold(M, dims, k) folds the matrix M to a tensor with
0015 %   its mode dimensions specified in dims along the k-th mode.
0016 %
0017 % $ History $
0018 %   - Created by Dahua Lin on Dec 17th, 2005
0019 %
0020 
0021 %% parse and verify
0022 if nargin < 2
0023     raise_lackinput('sltensor_fold', 3);
0024 end
0025 n = length(dims);
0026 if k < 1
0027     error('sltoolbox:invalidarg', ...
0028         'The mode index should be positive');
0029 elseif k > n
0030     error('sltoolbox:argmismatch', ...
0031         'The mode index exceeds the tensor order');
0032 end
0033 if numel(M) ~= prod(dims)
0034     error('sltoolbox:argmismatch', ...
0035         'The size of matrix and the dimensions of tensor do not match');
0036 end
0037 
0038 %% compute
0039 if k == 1
0040     T = reshape(M, dims);
0041 else
0042     if k < n
0043         pdims = [k, 1:k-1, k+1:n];
0044     else
0045         pdims = [k, 1:k-1];
0046     end
0047     T = reshape(M, dims(pdims));
0048     T = ipermute(T, pdims);
0049 end
0050

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