agg, groupBy, rollup
Other SparkDataFrame functions: SparkDataFrame-class,
  agg, alias,
  arrange, as.data.frame,
  attach,SparkDataFrame-method,
  broadcast, cache,
  checkpoint, coalesce,
  collect, colnames,
  coltypes,
  createOrReplaceTempView,
  crossJoin, dapplyCollect,
  dapply, describe,
  dim, distinct,
  dropDuplicates, dropna,
  drop, dtypes,
  except, explain,
  filter, first,
  gapplyCollect, gapply,
  getNumPartitions, group_by,
  head, hint,
  histogram, insertInto,
  intersect, isLocal,
  isStreaming, join,
  limit, localCheckpoint,
  merge, mutate,
  ncol, nrow,
  persist, printSchema,
  randomSplit, rbind,
  registerTempTable, rename,
  repartition, rollup,
  sample, saveAsTable,
  schema, selectExpr,
  select, showDF,
  show, storageLevel,
  str, subset,
  summary, take,
  toJSON, unionByName,
  union, unpersist,
  withColumn, withWatermark,
  with, write.df,
  write.jdbc, write.json,
  write.orc, write.parquet,
  write.stream, write.text