Github user felixcheung commented on a diff in the pull request: https://github.com/apache/spark/pull/9218#discussion_r43698343 --- Diff: R/pkg/R/DataFrame.R --- @@ -276,6 +276,75 @@ setMethod("names<-", } }) +#' @rdname columns +#' @name colnames +setMethod("colnames", + signature(x = "DataFrame"), + function(x) { + columns(x) + }) + +#' @rdname columns +#' @name colnames<- +setMethod("colnames<-", + signature(x = "DataFrame", value = "character"), + function(x, value) { + sdf <- callJMethod(x@sdf, "toDF", as.list(value)) + dataFrame(sdf) + }) + +rToScalaTypes <- new.env() +rToScalaTypes[["integer"]] <- "integer" # in R, integer is 32bit +rToScalaTypes[["numeric"]] <- "double" # in R, numeric == double which is 64bit +rToScalaTypes[["double"]] <- "double" +rToScalaTypes[["character"]] <- "string" +rToScalaTypes[["logical"]] <- "boolean" + +#' coltypes +#' +#' Set the column types of a DataFrame. +#' +#' @name coltypes +#' @param x (DataFrame) +#' @return value (character) A character vector with the target column types for the given +#' DataFrame. Column types can be one of integer, numeric/double, character, logical, or NA +#' to keep that column as-is. +#' @rdname coltypes +#' @aliases coltypes +#' @export +#' @examples +#'\dontrun{ +#' sc <- sparkR.init() +#' sqlContext <- sparkRSQL.init(sc) +#' path <- "path/to/file.json" +#' df <- jsonFile(sqlContext, path) +#' coltypes(df) <- c("character", "integer") +#' coltypes(df) <- c(NA, "numeric") +#'} +setMethod("coltypes<-", + signature(x = "DataFrame", value = "character"), + function(x, value) { + cols <- columns(x) + ncols <- length(cols) + if (length(value) == 0 || length(value) != ncols) { --- End diff -- It could do that. I would rather be concise even if only a few more lines because - it's already checking for length == 0 - not sure we could create a DataFrame with 0 col from R - no point to set column data type on a DataFrame having no column Thought?
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