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##########################################################################
## Utility Functions
##
## This software is distributed under the terms of the GNU GENERAL
## PUBLIC LICENSE Version 2, June 1991. See the package LICENSE
## file for more information.
##
## Copyright (C) 2003-2007 Andrew D. Martin and Kevin M. Quinn
## Copyright (C) 2007-present Andrew D. Martin, Kevin M. Quinn,
## and Jong Hee Park
##########################################################################
# takes a symmetric matrix x and returns lower diagonal
# note: does not check for symmetry
#
# ADM 4/18/2003
"vech" <-
function (x) {
x <- as.matrix(x)
if (dim(x)[1] != dim(x)[2]) {
stop("Non-square matrix passed to vech().\n")
}
output <- x[lower.tri(x, diag = TRUE)]
dim(output) <- NULL
return(output)
}
# takes vector x and returns an nrow times nrow symmetric matrix
# this will recycle the elements of x as needed to fill the matrix
#
# ADM 4/18/2003
# ADM 11/13/2003 [bug fix]
# ADM 1/25/2006 [patch to automatically compute matrix size]
"xpnd" <-
function (x, nrow = NULL) {
dim(x) <- NULL
if(is.null(nrow)) nrow <- (-1 + sqrt(1 + 8 * length(x))) / 2
output <- matrix(0, nrow, nrow)
output[lower.tri(output, diag = TRUE)] <- x
hold <- output
hold[upper.tri(hold, diag=TRUE)] <- 0
output <- output + t(hold)
return(output)
}
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