引用数据表列中循环中的数字

Question

我有一个像这样的数据集：

customer_id <- c("1","1","1","2","2","2","2","3","3","3")
account_id <- as.character(c(11,11,11,55,55,55,55,38,38,38))
time <- c(as.Date("2017-01-01","%Y-%m-%d"), as.Date("2017-02-01","%Y-%m-%d"), as.Date("2017-03-01","%Y-%m-%d"),
              as.Date("2017-12-01","%Y-%m-%d"), as.Date("2018-01-01","%Y-%m-%d"), as.Date("2018-02-01","%Y-%m-%d"),
              as.Date("2018-03-01","%Y-%m-%d"), as.Date("2018-04-01","%Y-%m-%d"), as.Date("2018-05-01","%Y-%m-%d"),
              as.Date("2018-06-01","%Y-%m-%d"))
tenor <- c(1,2,3,1,2,3,4,1,2,3)
variable_x <- c(87,90,100,120,130,150,12,13,15,14)

my_data <- data.table(customer_id,account_id,time,tenor,variable_x)

现在，我想创建新的变量“PD_Q1”直到“PD_Q20”，当“tenor”等于1到20时，它将等于“variable_x”的值，即，如果tenor = 1，则PD_Q1等于variable_x的值，如果tenor = 2等，PD_Q2等于variable_x的值，我想通过customer_id，account_id来做。我有代码，但只有PD_Q1和我想做一个循环遍历i = 1:20，其中我只改变tenor == i（这一个很容易）并在此循环中引用列PD_Qi这对我来说是一个问题。 i的一个值的代码在这里：

my_data[tenor == 1, PD_Q1_temp := variable_x, by = c("customer_id", "account_id")]

list_accs <- my_data[tenor == 1, c("customer_id", "account_id", "PD_Q1_temp")]

list_accs <- unique(list_accs, by = c("customer_id", "account_id"))

names(list_accs) = c("customer_id", "account_id", "PD_Q1")

my_data = merge(x = my_data, y = list_accs, by = c("customer_id", "account_id"), all.x = TRUE)

my_data$PD_Q1_temp <- NULL

现在，请问你如何建立一个从1到20的循环，其中，次级，PD_Q1_temp和PD_Q1会改变？具体来说，我不知道如何在循环中使用此i索引引用列名或变量。

i = 1和i = 2（创建变量PD_Q1和PD_Q2）的预期输出在此处：

> my_data
customer_id account_id       time tenor variable_x PD_Q1 PD_Q2

1: 1 11 2017-01-01 1 87 87 90 2: 1 11 2017-02-01 2 90 87 90 3: 1 11 2017-03-01 3 100 87 90 4: 2 55 2017-12-01 1 120 120 130 5: 2 55 2018-01-01 2 130 120 130 6: 2 55 2018-02-01 3 150 120 130 7: 2 55 2018-03-01 4 12 120 130 8: 3 38 2018-04-01 1 13 13 15 9: 3 38 2018-05-01 2 15 13 15 10: 3 38 2018-06-01 3 14 13 15

现在我想使用上面的代码在循环中创建PD_Q3，PD_Q4等，创建一个这样的变量。

Answer 1

你能展示你的预期产量吗？

我想你可以用tidyr::gather()做你想做的事：

library(dplyr)
library(tidyr)

my_data %>%
  tbl_df() %>%
  select(-time) %>%
  mutate(tenor = paste0("PD_Q", tenor)) %>%
  spread(tenor, variable_x)

# # A tibble: 3 x 6
#   customer_id account_id PD_Q1 PD_Q2 PD_Q3 PD_Q4
#   <chr>       <chr>      <dbl> <dbl> <dbl> <dbl>
# 1 1           11            87    90   100    NA
# 2 2           55           120   130   150    12
# 3 3           38            13    15    14    NA