Question

例如，我有变量

Store.Number <- c("105, 105, 105, 106, 106, 106, 110, 110, 110, 110")
Date <- c("2017-01-04", "2016-07-06", "2016-04-04", "2017-01-31", "2016-10-31", 
          "2016-05-11", "2017-01-26", "2016-10-28", "2016-07-20", "2016-04-27")
Jan012016 <- c("369",NA,NA.......)
a <- as.Date("01/01/2016", "%m/%d/%Y)

我想编写一个函数，使第一个循环检查

for i=1
Store.Number[i+1,1] = Store.Number [i,1]
If "True"
abs(Date[i,2] - Date[i+1,2])
Else
abs(Date[i,2] - a)

示例：

Store.Number[2,1] = Store.Number [1,1] > TRUE
Jan012016 = abs(Date[2,2] - Date[1,2])

Else
Jan012016 = abs(Date[i,2] - a)

Answer 1

R中最常用于将数据拆分为子集并执行计算的函数可能是tapply和aggregate。在这种情况下，tapply给出的输出最接近您想要的输出，例如：

Store.Number <- c(105, 105, 105, 106, 106, 106, 110, 110, 110, 110)
Date <- as.Date(c("2017-01-04", "2016-07-06", "2016-04-04", "2017-01-31", "2016-10-31", 
          "2016-05-11", "2017-01-26", "2016-10-28", "2016-07-20", "2016-04-27"), "%Y-%m-%d")
a <- as.Date("01/01/2016", "%m/%d/%Y")

store.diffs <- tapply(Date, Store.Number, function(x)abs(diff(c(a,x))))
Jan012016 <- do.call(c,store.diffs)
names(Jan012016) <- NULL
Jan012016
# Time differences in days
# [1] 369 182  93 396  92 173 391  90 100  84

请注意，我已删除了Store.Number定义中的引号，并将Date从字符转换为日期。

我想在R中创建一个嵌套函数

1 个答案: