如果匹配，则在数据框列上使用ifelse替换为日期时间列值 [英] ifelse on data frame column to replace with date time column values if matched

问题描述

我需要帮助。我正在尝试根据 txt_col 列的匹配值将 date_time 列值复制到新列中匹配标记为 NA 。这是我的代码：

I need help. I am trying to copy the date_time column values into new column based on matching values of txt_col column and those that are not matched mark as NA. Here is my code:

df$new_col <- ifelse(df$txt_col == "apple", df$date_time, NA)

但是，我在新列中得到数字，而不是日期时间：

However, I get numbers in the new column, instead of date-time :

   new_col
1477962000
1451755980
1451755980
1451755980

查看 str（df）时，列 date_time 是 POSIXct 。我试图将 as.numeric 和 POSIXct 转换，但是没有用。如果您有更优雅的方式来完成我要达到的目标，那么如果您分享的话，将不胜感激。谢谢。

When looking at the str(df), the column date_time is POSIXct. I tried to convert as.numeric and POSIXct, it didn't work. If you have more elegant ways to do what I am trying to achieve, it would be much appreciated if you share. Thank you.

推荐答案

将 dplyr 打包为更严格的功能 if_else 验证true和false组件的类。显式提供NA值的类别使此类型更加安全

Package dplyr as a stricter function if_else that verifies the classes of both the true and false components. Explicitly providing the class for the NA value makes this more "type safe"

library(dplyr)
df <- data.frame(txt_col = c("apple", "apple", "orange"),
                 date_time = as.POSIXct(c("2017-01-01", "2017-01-02", "2017-01-03")))

# use dplyr::if_else instead, and provide explicit class
df$new_col <- if_else(df$txt_col == "apple", df$date_time, as.POSIXct(NA))

df
#   txt_col  date_time    new_col
# 1   apple 2017-01-01 2017-01-01
# 2   apple 2017-01-02 2017-01-02
# 3  orange 2017-01-03       <NA>

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