Question

如何计算在＆＃34; long＆＃34;中按用户ID分组的多个变量之间的差值。数据框架？

数据格式：

d1 <- data.frame(
    id = rep(c(1, 2, 3, 4, 5), each = 2),
    purchased = c(rep(c(T, F), 3), F, T, T, F), 
    product = rep(c("A", "B"), 5), 
    grade = c(1, 2, 1, 2, 2, 3, 7, 5, 1, 2),
    rate = c(10, 12, 10, 12, 12, 14, 22, 18, 10, 12),
    fee = rep(c(1, 2), 5))

这是我的迂回解决方案：

dA <- d1 %>%
    filter(product == "A")

dB <- d1 %>%
    filter(product == "B")

d2 <- inner_join(dA, dB, by = "id", suffix = c(".A", ".B"))

d3 <- d2 %>% 
    mutate(
        purchased = if_else(purchased.A == T, "A", "B"),
        dGrade = grade.B - grade.A, 
        dRate = rate.B - rate.A, 
        dFee = fee.B - fee.A) %>%
    select(id, purchased:dFee)

所有这些看起来都非常低效和复杂。这里适用tidyr::spread或其他dplyr / tidyr函数吗？（我无法继续工作）......

Answer 1

我们可以使用gather/spread执行此操作。使用gather将数据从“宽”重塑为“长”，按“id”，“Var”分组，我们根据逻辑列“购买”得到“产品”，得到'Val'的差异对于“B”和“A”的“产品”，以及从“长”到“宽”格式的spread。

library(dplyr)
library(tidyr)
gather(d1, Var, Val, grade:fee) %>% 
           group_by(id, Var) %>% 
           summarise(purchased = product[purchased], 
                     Val = Val[product == 'B'] - Val[product == 'A'])%>% 
           spread(Var, Val)
#     id purchased   fee grade  rate
#   <dbl>    <fctr> <dbl> <dbl> <dbl>
#1     1         A     1     1     2
#2     2         A     1     1     2
#3     3         A     1     1     2
#4     4         B     1    -2    -4
#5     5         A     1     1     2

OP的输出（'d3'）是

d3
#  id purchased dGrade dRate dFee
#1  1         A      1     2    1
#2  2         A      1     2    1
#3  3         A      1     2    1
#4  4         B     -2    -4    1
#5  5         A      1     2    1

计算按用户ID分组的多个变量之间的差值

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