The value of the third row of mtcars$mpg
is 22.8
.
library(tidyverse)
mtcars$mpg[[3]]
I go ahead and replace this 22.8
with the value 5,555
as shown below. It works but not at the third row as I command my computer to do! Instead the value shows up at the 22nd row of the mtcars$mpg
column.
mtreplace <- mtcars %>% mutate(mpg = replace(mpg, mpg[[3]], 5555))
mtreplace
mtreplace$mpg[[3]]
mtreplace$mpg[[22]]
How do I get this change to occur at precisely the third row of mtcars$mpg
? And what went wrong?
该代码应为
mtcars %>% mutate(mpg = replace(mpg, 3, 5555))
I think dplyr is probably overkill, and may not be the best tool for this issue. This works fine:
mtcars[3, "mpg"] <- 5555
Also worth bearing in mind that for a numeric vector, you should use single [. The [[ is for lists when you want to get an element and not a range of elements (ie you don't want another list).
We can use
library(dplyr)
mtcars %>%
mutate(mpg = case_when(row_number() == 3 ~ 5555, TRUE ~ mpg))
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.