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#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# group.R - GroupedData class and methods implemented in S4 OO classes
setOldClass("jobj")
#' @title S4 class that represents a GroupedData
#' @description GroupedDatas can be created using groupBy() on a DataFrame
#' @rdname GroupedData
#' @seealso groupBy
#'
#' @param sgd A Java object reference to the backing Scala GroupedData
#' @export
setClass("GroupedData",
slots = list(sgd = "jobj"))
setMethod("initialize", "GroupedData", function(.Object, sgd) {
.Object@sgd <- sgd
.Object
})
#' @rdname DataFrame
groupedData <- function(sgd) {
new("GroupedData", sgd)
}
#' @rdname show
setMethod("show", "GroupedData",
function(object) {
cat("GroupedData\n")
})
#' Count
#'
#' Count the number of rows for each group.
#' The resulting DataFrame will also contain the grouping columns.
#'
#' @param x a GroupedData
#' @return a DataFrame
#' @export
#' @examples
#' \dontrun{
#' count(groupBy(df, "name"))
#' }
setMethod("count",
signature(x = "GroupedData"),
function(x) {
dataFrame(callJMethod(x@sgd, "count"))
})
#' Agg
#'
#' Aggregates on the entire DataFrame without groups.
#' The resulting DataFrame will also contain the grouping columns.
#'
#' df2 <- agg(df, <column> = <aggFunction>)
#' df2 <- agg(df, newColName = aggFunction(column))
#'
#' @param x a GroupedData
#' @return a DataFrame
#' @rdname agg
#' @examples
#' \dontrun{
#' df2 <- agg(df, age = "sum") # new column name will be created as 'SUM(age#0)'
#' df2 <- agg(df, ageSum = sum(df$age)) # Creates a new column named ageSum
#' }
setGeneric("agg", function (x, ...) { standardGeneric("agg") })
setMethod("agg",
signature(x = "GroupedData"),
function(x, ...) {
cols = list(...)
stopifnot(length(cols) > 0)
if (is.character(cols[[1]])) {
cols <- varargsToEnv(...)
sdf <- callJMethod(x@sgd, "agg", cols)
} else if (class(cols[[1]]) == "Column") {
ns <- names(cols)
if (!is.null(ns)) {
for (n in ns) {
if (n != "") {
cols[[n]] = alias(cols[[n]], n)
}
}
}
jcols <- lapply(cols, function(c) { c@jc })
# the GroupedData.agg(col, cols*) API does not contain grouping Column
sdf <- callJStatic("org.apache.spark.sql.api.r.SQLUtils", "aggWithGrouping",
x@sgd, listToSeq(jcols))
} else {
stop("agg can only support Column or character")
}
dataFrame(sdf)
})
# sum/mean/avg/min/max
methods <- c("sum", "mean", "avg", "min", "max")
createMethod <- function(name) {
setMethod(name,
signature(x = "GroupedData"),
function(x, ...) {
sdf <- callJMethod(x@sgd, name, toSeq(...))
dataFrame(sdf)
})
}
createMethods <- function() {
for (name in methods) {
createMethod(name)
}
}
createMethods()
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