R/whatis.R

In YaleToolkit: Data exploration tools from Yale University.

"whatis" <-
function(x, var.name.truncate = 20, type.truncate = 14) {
 
  if (!is.data.frame(x)) {
    x <- data.frame(x)
    warning("Object coerced to a data frame.\n")
  }
  if ( is.na(length(dim(x))) | is.null(length(dim(x))) )
    stop("You can not be serious!\n")

  sum.na <- function(y) sum(y, na.rm=TRUE)

  size <- dim(x)
  is.fac <- unlist(lapply(x, is.factor))
  is.char <- unlist(lapply(lapply(x, as.vector), is.character))
  is.fc <- is.fac | is.char
  is.ord <- unlist(lapply(x, is.ordered))

  sum.var.na <- apply(is.na(x), 2, sum)

  is.mixed <- rep(TRUE, size[2])
  this.type <- rep("", size[2])
  num.values <- rep(0, size[2])
  summ <- matrix(NA,size[2],2) 
  summ <- as.data.frame(summ)
  names(summ) <- c("min","max")
  precision <- rep(NA,size[2])
  var.abbrev <- rep('',size[2])
  #uniquifier <- 1

  for (i in 1:(size[2])) {

    if (nchar(names(x)[i]) > var.name.truncate) {
       #var.abbrev[i] <- paste(substr(names(x)[i], 1, 15), '...',
       #                       uniquifier, sep = '')
       #uniquifier <- uniquifier + 1
      var.abbrev[i] <- paste(substr(names(x)[i], 1, var.name.truncate), 
                             '&', sep="")
    } else var.abbrev[i] <- names(x)[i]

    num.values[i] <- length(table(x[,i]))

    z <- as.character(x[,i])
    has.nonnumeric <- (regexpr("[^0-9.-]", gsub(" ", "", z), perl=TRUE) > 0)
    has.numeric <- (regexpr("[0-9.-]", gsub(" ", "", z), perl=TRUE) > 0)
    is.mixed[i] <- sum.na(has.nonnumeric)>0 & sum.na(has.numeric)>0

    if (is.fac[i] & !is.mixed[i]) this.type[i] <- "pure factor"
    if (is.fac[i] & is.mixed[i])  this.type[i] <- "mixed factor"
    if (is.ord[i])                this.type[i] <- "ordered factor"
    if (is.char[i] & !is.fac[i])  this.type[i] <- "character"
    if (!is.char[i] & !is.fac[i]) this.type[i] <- "numeric"

    xtemp <- x[!is.na(x[,i]),i]
    if (length(xtemp)==0) {
      summ[i,] <- rep(NA, 2)
      precision[i] <- NA
    } else {

      if (this.type[i] == "numeric") {
        z <- as.character(x[,i])
        has.decimal <- as.vector(regexpr('.', z, fixed=TRUE))
        has.decimal[is.na(has.decimal)] <- 0
        has.decimal[has.decimal<0] <- 0
        has.decimal[has.decimal>0] <- nchar(z[has.decimal>0]) - has.decimal[has.decimal>0]
        precision[i] <- 10^(-1*max(has.decimal[!is.na(has.decimal)]))
      }

      if (this.type[i]=="numeric")
        summ[i,] <- c(min(x[,i], na.rm=TRUE), max(x[,i], na.rm=TRUE))
      if (this.type[i]!="numeric")
        summ[i,] <- sort(as.character(x[,i]))[c(1,length(xtemp))] 

    }
  }

  summary.by.variable <- data.frame(variable.name=var.abbrev, 
                                    type=substring(this.type, 1, type.truncate),
                                    missing=sum.var.na,
                                    distinct.values=num.values,
                                    precision=precision)
  summary.by.variable <- cbind(summary.by.variable, summ)
  row.names(summary.by.variable) <- 1:ncol(x)
 
  return(summary.by.variable) 

}