Github user shivaram commented on a diff in the pull request:
https://github.com/apache/spark/pull/9613#discussion_r45796525
--- Diff: R/pkg/R/DataFrame.R ---
@@ -2151,3 +2151,97 @@ setMethod("coltypes",
rTypes
})
+
+#' Display the structure of a DataFrame, including column names, column
types, as well as a
+#' a small sample of rows.
+#' @name str
+#' @title Compactly display the structure of a dataset
+#' @rdname str
+#' @family DataFrame functions
+#' @param object a DataFrame
+#' @examples \dontrun{
+#' # Create a DataFrame from the Iris dataset
+#' irisDF <- createDataFrame(sqlContext, iris)
+#'
+#' # Show the structure of the DataFrame
+#' str(irisDF)
+#' }
+setMethod("str",
+ signature(object = "DataFrame"),
+ function(object) {
+
+ # TODO: These could be made global parameters, though in R
it's not the case
+ MAX_CHAR_PER_ROW <- 120
+ MAX_COLS <- 100
+
+ # Get the column names and types of the DataFrame
+ names <- names(object)
+ types <- coltypes(object)
+
+ # Get the number of rows.
+ # TODO: Ideally, this should be cached
+ cachedCount <- nrow(object)
+
+ # Get the first elements of the dataset. Limit number of
columns accordingly
+ localDF <- if (ncol(object) > MAX_COLS) {
+ head(object[, c(1:MAX_COLS)])
+ } else {
+ head(object)
+ }
+
+ # The number of observations will be displayed only if the
number
+ # of rows of the dataset has already been cached.
+ if (!is.null(cachedCount)) {
+ cat(paste0("'", class(object), "': ", cachedCount, " obs. of
",
+ length(names), " variables:\n"))
+ } else {
+ cat(paste0("'", class(object), "': ", length(names), "
variables:\n"))
+ }
+
+ # Whether the ... should be printed at the end of each row
+ ellipsis <- FALSE
+
+ # Add ellipsis (i.e., "...") if there are more rows than shown
+ if (!is.null(cachedCount) && (cachedCount > 6)) {
+ ellipsis <- TRUE
+ }
+
+ if (nrow(localDF) > 0) {
+ for (i in 1 : ncol(localDF)) {
+ firstElements <- ""
+
+ # Get the first elements for each column
+ if (types[i] == "character") {
+ firstElements <- paste(paste0("\"", localDF[,i], "\""),
collapse = " ")
+ } else {
+ firstElements <- paste(localDF[,i], collapse = " ")
+ }
+
+ # Add the corresponding number of spaces for alignment
+ spaces <- paste(rep(" ", max(nchar(names) -
nchar(names[i]))), collapse="")
+
+ # Get the short type. For 'character', it would be 'chr';
+ # 'for numeric', it's 'num', etc.
--- End diff --
We have a 100 char line limit. I think the comments here or in line 2230
should fit in one line ?
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