sptendiag.m

张量分析工具

function X = sptendiag(v,sz)
%SPTENDIAG Creates a sparse tensor with v on the diagonal.
%
%   SPTENDIAG(V) creates a sparse tensor with N dimensions, each of
%   size N, where N is the number of elements of V. The elements of V
%   are placed on the superdiagonal.
%
%   SPTENDIAG(V,SZ) is the same as above but creates a tensor of size
%   SZ. If SZ is not big enough, the tensor will be enlarged to
%   accommodate the elements of V on the superdiagonal.
%
%   Examples
%   X = sptendiag([0.1 0.22 0.333]) %<-- creates a 3x3x3 sptensor
%
%   See also SPTENSOR, TENDIAG.
%
%MATLAB Tensor Toolbox.
%Copyright 2007, Sandia Corporation. 

% This is the MATLAB Tensor Toolbox by Brett Bader and Tamara Kolda. 
% http://csmr.ca.sandia.gov/~tgkolda/TensorToolbox.
% Copyright (2007) Sandia Corporation. Under the terms of Contract
% DE-AC04-94AL85000, there is a non-exclusive license for use of this
% work by or on behalf of the U.S. Government. Export of this data may
% require a license from the United States Government.
% The full license terms can be found in tensor_toolbox/LICENSE.txt
% $Id: sptendiag.m,v 1.5 2007/01/10 01:27:30 bwbader Exp $

% Make sure v is a column vector
v = reshape(v,[numel(v) 1]);

N = numel(v);
if ~exist('sz','var')
    sz = repmat(N,1,N);
end

X = sptensor(sz);
subs = repmat((1:N)', 1, length(sz));
X(subs) = v;