R/wideByFactor.R

In gdata: Various R Programming Tools for Data Manipulation

wideByFactor <- function(x, factor, common, sort=TRUE, keepFactor=TRUE)
{
  ## Setup
  if(!is.data.frame(x))
    stop("'x' must be a data frame")
  if(length(factor) != 1)
    stop("'factor' can be only of length one")
  if(!is.factor(x[[factor]]))
    stop("column defined in 'factor' must be a factor")
  if(sort) x <- x[order(x[[factor]]), ]

  ## Extend by factors levels
  y <- x[common]
  if(keepFactor) y[factor] <- x[factor]
  levs <- levels(x[[factor]])

  ## Remove common and factor from the list of column names
  other <- names(x)
  other <- other[!(other %in% common) & !(other %in% factor)]

  ## Add all other columns but as a set for each level of a factor
  for(level in levs) {
    for(col in other) {
      ## Add a column col
      y[paste(col, level, sep=".")] <- x[col]
      ## Fill with NA for other levels than level
      y[x[factor] != level, paste(col, level, sep=".")] <- NA
      ## This filling might be inefficient if there is large number
      ## of levels, since there will be quite a lot of filling.
    }
  }
  y
}