use_case_3.r

data_dt_lazy <- lazy_dt(data_dt, immutable=FALSE)

mbm <- microbenchmark("dplyr" = { 
                                    result_df <- data_df %>% 
                                                 filter(amount <= 4000) %>% 
                                                 mutate(order_value = amount * price) %>% 
                                                 group_by(id) %>% 
                                                 summarise(avg_order_value = mean(order_value)) 
                                },
                      "data.table" = { 
                                    result_dt <- data_dt[amount <= 4000][, order_value := amount * price][, .(avg_order_value = mean(order_value)), keyby = id]
                                     },
                      "dtplyr" = { 
                                    result_dtplyr <- data_dt_lazy %>% 
                                                     filter(amount <= 4000) %>% 
                                                     mutate(order_value = amount * price) %>% 
                                                     group_by(id) %>% 
                                                     summarise(avg_order_value = mean(order_value))  %>%
                                                     as.data.table()
                                  })

mbm