A rewrite of ddply's summarize that 'flattens' named columns

flat-summarize.R

# Fork of ddply's summarize that 'flattens' named columns
flat.summarize <- function (data, ...) {
  stopifnot(is.data.frame(data) || is.list(data) || is.environment(data))
  cols <- as.list(substitute(list(...))[-1])
  if (is.null(names(cols))) {
    missing_names <- rep(TRUE, length(cols))
  }
  else {
    missing_names <- names(cols) == ""
  }
  if (any(missing_names)) {
    names <- unname(unlist(lapply(match.call(expand.dots = FALSE)$..., 
                                  deparse)))
    names(cols)[missing_names] <- names[missing_names]
  }
  data <- as.list(data)
  for (col in names(cols)) {
    res <- eval(cols[[col]], data, parent.frame())
    # addition from original summarize so that it accepts functions
    # returning more than one named columns
    if(length(res) > 1) {
      for(name in names(res)) {
        col.name <- paste(col, name, sep='.')
        col.res  <- res[[name]]
        # add in cols for quickdf
        cols[[col.name]] <- col.res
        data[[col.name]] <- col.res
      }
      # rm the base col
      cols <- cols[names(cols)!=col]
    } else {
      data[[col]] <- eval(cols[[col]], data, parent.frame())
    }
  }
  quickdf(data[names(cols)])
}