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# These functions are
# Copyright (C) 1998-2012 T.W. Yee, University of Auckland.
# All rights reserved.
s <- function(x, df = 4, spar = 0, ...) {
xs <- substitute(x)
ans <- as.character(xs)
if (length(ans) > 1)
stop("x argument must be of length one")
call <- deparse(sys.call())
if (ncol(as.matrix(x)) > 1)
stop("x must be a vector")
if (!is.null(levels(x))) {
x <- if (is.ordered(x)) {
as.vector(x)
} else
stop("unordered factors cannot be used as smoothing variables")
}
attr(x, "spar") <- spar
attr(x, "df") <- df
attr(x, "call") <- call
attr(x, "class") <- "smooth"
attr(x, "s.xargument") <- ans # Needed for prediction and constraints
a <- is.na(x)
if (any(a))
attr(x, "NAs") <- seq(along = x)[a]
x
}
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