How to generate A LIST OF datasets & graphs and EXPORTING them?

Question

Here is the dataset :

# dataset call DT
DT <- data.table(
Store = rep(c("store_A","store_B","store_C","store_D","store_E"),4),
Amount = sample(1000,20))

I have TWO targets have to achieve :

• 1.Generate INDEPENDENT Grouped dataset for exporting EXCEL.CSV files.
• 2.Generate INDEPENDENT Graph for exporting PNG files.

*Not Necessary to run both in one operation.

Constraints : I can only perform these with ONE by ONE basic operation like :

# For dataset & CSV export
store_A <- DT %>% group_by(Store) %>% summarise(Total = sum(Amount))

fwrite(store_A,"PATH/store_A.csv")

store_B <- DT %>% group_by(Store) %>% summarise(Total = sum(Amount))

fwrite(store_B,"PATH/store_A.csv")
.....
# For graph :

Plt_A <- ggplot(store_A,aes(x = Store, y = Total)) + geom_point()

ggsave("PATH/Plt_A.png")

Plt_B <- ggplot(store_B,aes(x = Store, y = Total)) + geom_point()

ggsave("PATH/Plt_B.png")
.....

*Approaches written by ' for - loops ' can be found but confusing which is more efficient and WORKS in generate graph, for loops VS lapply family -- As real dataset has over 2 millions rows 70 cols and 10k groups to generate, for loops maybe runned terribly SLOW and crash R itself. The bottleneck in actual dataset contains 10k of "Store" groups.

Answer 1

As everything needs to be in loop:

require(tidyverse)
require(data.table)

setwd("Your working directory")

# dataset call DT
DT <- data.table(
  Store = rep(c("store_A","store_B","store_C","store_D","store_E"),4),
  Amount = sample(1000,20)) %>% 
  #Arrange by store and amount
  arrange(Store, Amount) %>% 
  #Nesting by store, thus the loop counter/index will go by store
  nest(-Store)

#Export CSVs by store
i <- 1
for (i in 1:nrow(DT)) {
    write.csv(DT$data[i], paste(DT$Store[i], "csv", sep = "."))
  }

#Export Graphs by store
i <- 1
for (i in 1:nrow(DT)) {
  Graph <- DT$data[i] %>% 
    as.data.frame() %>%
    ggplot(aes(Amount)) + geom_histogram()

  ggsave(Graph, file = paste0(DT$Store[i],".png"), width = 14, height = 10, units = "cm")

}