“％m％" mapply运算符 [英] "%m %" operator with mapply

问题描述

我正在尝试使用mapply在数据框的a和b列中向当前日期添加月份.这是创建示例数据框的代码:

I am trying to use mapply to add months to the current dates in columns a and b of my dataframe. Here is the code to create a sample data frame:

library(lubridate)
a <- as.Date(c("2012-01-11","2012-06-30","2012-04-18"))
b <- as.Date(c("2013-04-21","2012-03-22","2012-05-01"))
df <- data.frame(a,b)

我可以使用mapply("+",df, c(30,30))将30天添加到两列日期中.但是，当我尝试使用命令mapply("%m+%",df, months(1:2))时，我收到错误消息:

I can use mapply("+",df, c(30,30)) to add 30 days to both columns of dates. However, when I try to use the command mapply("%m+%",df, months(1:2)) I get the error message:

.setupMethodsTables(fdef，initialize = TRUE)中的错误:没有插槽 类"derivedDefaultMethod"的该对象的名称"group"

Error in .setupMethodsTables(fdef, initialize = TRUE) : no slot of name "group" for this object of class "derivedDefaultMethod"

是否可以通过％m +％运算符使用mapply?

Is it possible to use mapply with the %m+% operator?

推荐答案

在我对S4不了解的人看来，这与lubridate软件包和%m+%方法的构造方式有关.

To my S4 ignorant eyes, this appears to be an issue with the lubridate package and the way the %m+% method is constructed.

查看源

未导出的函数.quick_month_add似乎可以满足您的要求

It appears that the unexported function .quick_month_add will do what you want

 mapply(lubridate:::.quick_month_add,df,months(1:2), SIMPLIFY = FALSE)
$a
[1] "2012-01-11" "2012-06-30" "2012-04-18"

$b
[1] "2013-04-21" "2012-03-22" "2012-05-01"

请注意，必须将SIMPLIFY设置为FALSE，否则当简化为矩阵时，由于Date类被剥离，因此您将获得数字矩阵.

note that SIMPLIFY must be set to FALSE otherwise you will get numeric matrix as the Date class is stripped when simplifying to a matrix.

或者，Map(lubridate:::.quick_month_add,df,months(1:2))

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