Revision 04bbc417cf2927b827660bc07743429783569aec authored by HwB on 10 February 2013, 00:00:00 UTC, committed by Gabor Csardi on 10 February 2013, 00:00:00 UTC
1 parent 0e3ae6b
tri.Rd
\name{tri}
\alias{tril}
\alias{triu}
\title{
Triangular Matrices (Matlab Style)
}
\description{
Extract lower or upper triangular part of a matrix.
}
\usage{
tril(M, k = 0)
triu(M, k = 0)
}
\arguments{
\item{M}{numeric matrix.}
\item{k}{integer, indicating a secondary diagonal.}
}
\details{
\code{tril}\cr
Returns the elements on and below the kth diagonal of X, where k = 0 is
the main diagonal, k > 0 is above the main diagonal, and k < 0 is below
the main diagonal.
\code{triu}\cr
Returns the elements on and above the kth diagonal of X, where k = 0 is
the main diagonal, k > 0 is above the main diagonal, and k < 0 is below
the main diagonal.
}
\value{
Matrix the same size as the input matrix.
}
\note{
For \code{k==0} it is simply an application of the R functions
\code{lower.tri} resp. \code{upper.tri}.
}
\seealso{
\code{\link{Diag}}
}
\examples{
tril(ones(4,4), +1)
# 1 1 0 0
# 1 1 1 0
# 1 1 1 1
# 1 1 1 1
triu(ones(4,4), -1)
# 1 1 1 1
# 1 1 1 1
# 0 1 1 1
# 0 0 1 1
}
\keyword{ array }
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