R/divide_df.R

In datadr: Divide and Recombine for Large, Complex Data

getDivideDF <- function(data, by, postTransFn, bsvFn, update = FALSE) {
  d <- data.table(data)
  # convert factors to strings
  factorInd <- which(sapply(d, is.factor))
  for(i in seq_along(factorInd)) {
    d[[factorInd[i]]] <- as.character(d[[factorInd[i]]])
  }

  nms <- names(d)
  # d$i <- seq_len(nrow(b))
  setkeyv(d, by$vars)

  keyCols <- format(as.matrix(unique(d, by = key(d))[, by$vars, with = FALSE]),
    scientific = FALSE, trim = TRUE, justify = "none")
  keys <- apply(keyCols, 1, function(x) paste(paste(by$vars, "=", x, sep = ""), collapse = "|"))

  res <- vector("list", length(keys))

  ii <- 0
  ff <- function(dt) {
    ii <<- ii + 1
    res[[ii]] <<- list()
    res[[ii]]$key <<- keys[ii]
    res[[ii]]$value <<- addSplitAttrs(data.frame(dt), bsvFn, by, postTransFn)
    1
  }

  tmp <- d[, ff(.SD), by = key(d), .SDcols = nms]

  if(is.data.frame(res[[1]]$value)) {
    res <- ddf(res)
  } else {
    res <- ddo(res)
  }

  if(update)
    res <- updateAttributes(res)

  # add an attribute specifying how it was divided
  res <- setAttributes(res, list(div = list(divBy = by)))

  # add bsv attributes
  if(!is.null(bsvFn)) {
    desc <- getBsvDesc(kvExample(res)[[2]], bsvFn)
    tmp <- list(bsvFn = bsvFn, bsvDesc = desc)
    class(tmp) <- c("bsvInfo", "list")
    res <- setAttributes(res, list(bsvInfo = tmp))
  }

  res
}