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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{tr}
\alias{tr}
\title{trace}
\description{
This function returns the trace of an n-by-n square matrix x, defined to be the sum of the elements
on the main diagonal (the diagonal from the upper left to the lower right).
}
\usage{
tr(x)
}
\arguments{
\item{x}{an input matrix. Must be square}
}
\details{
The input matrix must be square.
}
\seealso{
\code{\link{vech}}, \code{\link{rvectorize}}, \code{\link{cvectorize}}
}
\examples{
tr(matrix(1:9, 3, 3))
tr(matrix(1:12, 3, 4))
}
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