r - 为什么使用 bind_rows 不在 show_query() 中运行

Question

如何获取 data.table 格式的最终​​查询？

如果不可能：如何将查询从 dplyr 重写为 data.table ？

library(data.table)
library(dplyr)
library(dtplyr)

#Data    
    dt = structure(list(Year = c(2015L, 2016L, 2017L, 2015L, 2016L, 2017L),
                        Item = c("Soybeans", "Soybeans", "Soybeans", "Pulses, Total", "Pulses, Total", "Pulses, Total"), 
                        Value = c(884688L, 829166L, 960640L, 2219455L, 2354696L, 2683772L)),
                   row.names = c(NA, -6L), class = "data.frame")
    
# query in  dplyr  
    dt %>% 
      group_by(Year) %>% 
      summarise(Value = sum(Value), Item = "Total") %>% 
      bind_rows(., dt) 
    
#conveert query to data.table    
    dtl=lazy_dt(dt)
    dtl %>% 
      group_by(Year) %>% 
      summarise(Value = sum(Value), Item = "Total") %>%
      bind_rows(., dtl) %>% show_query()

错误：参数 1 必须是数据帧或命名的原子向量。

Answer 1

使用data.table您可以将此操作编写为 -

library(data.table)

setDT(dt)
rbind(dt[, .(Value = sum(Value), Item = "Total"), Year], dt)

#   Year   Value          Item
#1: 2015 3104143         Total
#2: 2016 3183862         Total
#3: 2017 3644412         Total
#4: 2015  884688      Soybeans
#5: 2016  829166      Soybeans
#6: 2017  960640      Soybeans
#7: 2015 2219455 Pulses, Total
#8: 2016 2354696 Pulses, Total
#9: 2017 2683772 Pulses, Total