在dplyr链中结转价值 [英] Carry value forward in dplyr chain

问题描述

假设我有下面的列

**CurrentStatus**
Current
NoChange
NoChange
NoChange
NoChange
Late

我要对其进行更改，以便如果该值为 NoChange，则使用先前的值。

I want to mutate it so that if the value is "NoChange" it uses the prior value.

我尝试过：

myDF %>% mutate(CurrentStatus = ifelse(CurrentStatus == "NoChange", lag(CurrentStatus), CurrentStatus)

这似乎不起作用-我认为这是因为它进行了矢量化计算，因此可以同时查看所有延迟。我需要它向前滚动。我想知道没有for循环的最有效方法是什么。我特别想避免for循环，因为有些分组变量没有显示出来，我需要注意。

That doesn't seem to work -- I think it's because it does a vectorized calculation so it looks at all the lags at the same time. I need it to "roll forward". I was wondering what's the most efficient way to do this without a for loop. I specifically want to avoid a for loop as there are some grouping variables not shown that I need to be mindful of.

谢谢！

推荐答案

我们可以将'NoChange'替换为 NA ，然后使用 fill

We can replace the 'NoChange' to NA and then use fill

library(tidyverse)
myDF %>%
    mutate(CurrentStatus = replace(CurrentStatus, CurrentStatus == "NoChange", NA)) %>%
    fill(CurrentStatus)
#  CurrentStatus
#1       Current
#2       Current
#3       Current
#4       Current
#5       Current
#6          Late

---

或另一种选择是 na.locf 来自 zoo

library(zoo)
myDF$CurrentStatus <-  with(myDF, na.locf(replace(CurrentStatus, 
              CurrentStatus == "NoChange", NA)))

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