How do you pivot data from a list of data frames in R?

Question

Let\'s say I have a list of data frames ldf:

df1 <- data.frame(date = c(1,2), value = c(4,5))
df2 <- data.frame(date = c(1,2), value = c(4,5))
ldf <- li         


        

Answer 1

You could use:

library(data.table)
dt1 <- rbindlist(ldf)
setkey(dt1,'date')
dt1[,list(value=sum(value)), by='date']
 date value
1:    1     8
2:    2    10