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%
% Copyright 2007-2018 by the individuals mentioned in the source code history
%
% Licensed under the Apache License, Version 2.0 (the "License");
% you may not use this file except in compliance with the License.
% You may obtain a copy of the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS,
% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
% See the License for the specific language governing permissions and
% limitations under the License.
\name{diag2vec}
\alias{diag2vec}
\title{Extract Diagonal of a Matrix}
\description{
Given an input matrix, \code{diag2vec} returns a column vector of the elements along the diagonal.
}
\usage{
diag2vec(x)
}
\arguments{
\item{x}{an input matrix.}
}
\details{
Similar to the function \code{\link{diag}}, except that the input argument is always
treated as a matrix (i.e., it doesn't have diag()'s functions of returning an Identity matrix from an nrow specification, nor to return
a matrix wrapped around a diagonal if provided with a vector). To get vector2matrix functionality, call \code{\link{vec2diag}}.
}
\seealso{
\code{\link{vec2diag}}
}
\examples{
diag2vec(matrix(1:9, nrow=3))
# [,1]
# [1,] 1
# [2,] 5
# [3,] 9
diag2vec(matrix(1:12, nrow=3, ncol=4))
# [,1]
# [1,] 1
# [2,] 5
# [3,] 9
}
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