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##' Converts strings to formula
##'
##' Converts a vector of predictors and a vector of responses (characters) i#nto
##' a formula expression.
##'
##'
##' @param y vector of predictors
##' @param x vector of responses
##' @return An object of class \code{formula}
##' @author Klaus K. Holst
##' @seealso \code{\link{as.formula}},
##' @keywords models utilities
##' @examples
##'
##' toformula(c("age","gender"), "weight")
##'
##' @export
toformula <- function (y = ".", x = ".")
{
xst <- x[1]
xn <- length(x)
if (xn > 1)
for (i in 2:length(x)) {
xst <- paste(xst, "+", x[i])
}
yst <- y[1]
yn <- length(y)
if (yn > 1) {
yst <- paste0("c(", yst)
for (i in 2:length(y)) {
yst <- paste0(yst, ", ", y[i])
}
yst <- paste0(yst, ")")
}
ff <- paste(yst, "~", xst)
return(as.formula(ff))
}
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