R/default.knots.r

In SemiPar: Semiparametic Regression

###### R-function: default.knots ##########

# Computes default knots for a given
# x vector.

# Last changed: 13 SEP 2000

default.knots <- function(x,num.knots)
{
   # Delete repeated values from x

   x <- unique(x)

   # Work out the default number of knots

   if (missing(num.knots))
   {
      n <- length(x)
      d <- max(4,floor(n/35))
      num.knots <- floor(n/d - 1)
   }

   nx <- names(x)
   x <- as.vector(x)
   nax <- is.na(x)
   if(nas <- any(nax))
      x <- x[!nax]

   knots <- seq(0,1,length=num.knots+2)[-c(1,num.knots+2)]
   knots <- quantile(x,knots)

   names(knots) <- NULL
 
   return(knots)
}

########## End of default.knots ##########