How to create a loop inside a loop in R - r

Question

I am new to R and I need some help in relation loops. I need to produce a huge amount to tables from one data set and I think that a loop inside a loop will solve the problem, but I am having problems getting the right result.
Lets say I have the following data set:
var1 <- c("A","A","A","A","B","B","B","B")
var2 <- c(1,2,1,2,1,2,1,2)
df <- data.frame(var1,var2)
And I want to extract the data in 4 tables:
Result of "A" & 1
Result of "A" & 2
Result of "B" & 1
Result of "B" & 2
I have this loop, but I cannot get the 4 tables. Can anyone help!
for (i in df$var1) {
dummy<- df%>%filter(var1 == i)
for (j in dummy$var2) {
nTab <- paste0("tab_", j, sep ="")
assign(nTab, dummy%>%filter (var2 == j))
}
}

Answer 1

Expanding on #Gregor's comment, and the question here,
Save all data frames in list to separate .csv files,
you can use Map() with the split() function to output the newly created dataframes to individual csv files:
Code:
s=split(df, f = paste(df$var1, df$var2, sep = "_"))
Map(write.csv,s, paste0("table_",names(s),".csv"),row.names=F)
which will write the csv's to your current working directory, with the names "table_A_1.csv", etc based on the value of var1 and var2.

Answer 2

We can split the data frame into several data frames based on two columns and store them in a list.
df_list <- split(df, f = list(df$var1, df$var2))
df_list
# $A.1
# var1 var2
# 1 A 1
# 3 A 1
#
# $B.1
# var1 var2
# 5 B 1
# 7 B 1
#
# $A.2
# var1 var2
# 2 A 2
# 4 A 2
#
# $B.2
# var1 var2
# 6 B 2
# 8 B 2
To save the data frames in the list, we can further use the lapply function.
lapply(names(df_list), function(x) write.csv(df_list[[x]], paste0(x, ".csv"), row.names = FALSE))
Where df_list[[x]] is the way to access individual data frames based on the name. paste0(x, ".csv") is to construct file directory.