在 data.table 中重新创建 dplyr 摘要

Question

出于好奇，有没有一种方法可以使用 data.table 而不是 dplyr 来重新创建 summary 输出？

dt1 <- data.table(
  uid=c("A00111", "A00112","A00113","A00211","A00212","A00213","A00214","A00311","A00312"),
  area=c("A001", "A001","A001","A002","A002","A002","A002","A003","A003"),
  price=c(325147,NA,596020,257409,241206,248371,261076,595218,596678),
  type=c("Type1","Type2","Type3","Type2","Type3","Type2","Type2","Type2","Type3"))

summary <- dt1 %>% group_by(area) %>% summarise(
    Total_Number = length(uid),
    Total_Number_Check = unique(length(uid)),
    Number_of_Type_1 = length(uid[type=="Type1"]),
    Mean_Price_Type_1 = mean(price[type=="Type1"],na.rm = TRUE),
    Number_of_Type_2 = length(uid[type=="Type2"]),
    Mean_Price_Type_2 = mean(price[type=="Type2"],na.rm = TRUE),
    Number_of_Type_3 = length(uid[type=="Type3"]),
    Mean_Price_Type_3 = mean(price[type=="Type3"],na.rm = TRUE))

Answer 1

下面是 data.table

上面@DavidArenburg 的评论是默认的总结方式data.table。

但是，我没有一次性创建摘要，因为您可能有超过 3 个 type 变量。如果是这样，则（手动）总结 >10 种类型是行不通的。它会变成一个长（无聊）的代码。

所以我先按地区汇总（DT1），然后再按地区AND按类型汇总。然后将第二次总结的结果转为宽格式（DT2），并将left-joined DT2转为DT1。

所以下面的代码适用于任意数量的区域和任意数量的类型。

library( data.table )
#summarise by area
DT1 <- dt1[ , .( Total_Number = .N, 
                 Total_Number_Check = uniqueN( uid ) ), 
            by = .(area)]
#summarise by area AND type and cast to wide format
DT2 <- dcast( dt1[ , .( Number_of = .N, 
                        Mean_Price = mean( price, na.rm = TRUE ) ), 
                   by = .(area, type)], 
              area ~ type, 
              value.var = c("Number_of", "Mean_Price") )
#join
DT1[DT2, on = .(area)]

#    area Total_Number Total_Number_Check Number_of_Type1 Number_of_Type2 Number_of_Type3 Mean_Price_Type1
# 1: A001            3                  3               1               1               1            325147
# 2: A002            4                  4              NA               3               1                NA
# 3: A003            2                  2              NA               1               1                NA
# Mean_Price_Type2 Mean_Price_Type3
# 1:                NA            596020
# 2:          255618.7            241206
# 3:          595218.0            596678

在 data.table 中重新创建 dplyr 摘要

Recreate dplyr summarise in data.table

r

dplyr

data.table

summarize