text: install.packages("sparklyr")
  install.packages("tidyverse")
  
  library(sparklyr)
  library(tidyverse)
  
  spark_install(version = "3.0.0")
  sc  <- spark_connect(master = "local")
  
  df1 <- as_tibble(iris)
  df  <- copy_to(sc, df1)
  
  print(class(df1))
  print(class(df))
  # df1 is a data.frame, df is a function
  # different colnames, one is in spark formatting vs. df
  
  df %>% select(Sepal_Length,Species) %>% head %>% print
  df %>% filter(Sepal_Length>5.5) %>% head %>% print
  df %>% select(Sepal_Length,Species) %>% filter(Sepal_Length>5.5) %>% head %>% print
  df2 <- df %>% group_by(Species) %>% summarize(mean = mean(Sepal_Length), count = n()) %>% head %>% print
  df2 <- df2 %>% group_by(Species) %>% summarize(mean = mean(Sepal_Length), count = n()) %>% head %>% print
  df2 %>% arrange(Species) %>% head %>% print
  