用R中的先前值迭代填充NA行 [英] Fill NA row with previous value iteratively in R

问题描述

假设您在给定的df的各个星期内都有这样的事情：

Say you have something like this across various weeks in a given df:

DoW Value
Mon 1234
Tue NA
Wed 5678
Thu 9123
Fri 4567
Sat 8912
Sun 3456

我想用星期一的对应周的值填充每个星期二的NA。我该怎么做，最好是用最少的代码？

I'd like to fill every Tuesday's NA with Monday's value of it's correspondent week. How can I do this, preferably with the least amount of code possible?

谢谢。

推荐答案

这怎么办？

mydf <- structure(list(DoW = c("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", 
"Sun"), Value = c(1234L, NA, 5678L, 9123L, 4567L, 8912L, 3456L
)), .Names = c("DoW", "Value"), class = "data.frame", row.names = c(NA, 
-7L))

tuesd_na <- which(mydf$DoW == "Tue" & is.na(mydf$Value))
mydf$Value[tuesd_na] <- mydf$Value[tuesd_na - 1]
mydf
#>   DoW Value
#> 1 Mon  1234
#> 2 Tue  1234
#> 3 Wed  5678
#> 4 Thu  9123
#> 5 Fri  4567
#> 6 Sat  8912
#> 7 Sun  3456

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