Summing the values of several R Lists based on a date key [duplicate]

Answer 1

We can use data.table

library(data.table)
rbindlist(list_df)[, lapply(.SD, sum), date]
#         date clicks impressions
#1: 2019-06-01      3          16
#2: 2019-06-02      3          14
#3: 2019-06-03    111         149

data

list_df <- mget(paste0("df", 1:2))