我有一个名为cleandata的数据帧，需要更改列age上的值。
我可以从dplyr中找到要用filter和select函数替换的值。
> str(cleantrain)
'data.frame': 891 obs. of 9 variables:
$ train$PassengerId: int 1 2 3 4 5 6 7 8 9 10 ...
$ survived : Factor w/ 2 levels "0","1": 1 2 2 2 1 1 1 1 2 2 ...
$ Title : Factor w/ 17 levels "Capt","Col","Don",..: 12 13 9 13 12 12 12 8 13 13 ...
$ fare : num 7.25 71.28 7.92 53.1 8.05 ...
$ sbsp : int 1 1 0 1 0 0 0 3 0 1 ...
$ parch : int 0 0 0 0 0 0 0 1 2 0 ...
$ alone : Factor w/ 2 levels "0","1": 1 1 2 1 2 2 2 1 1 1 ...
$ familysize : Factor w/ 9 levels "1","2","3","4",..: 2 2 1 2 1 1 1 5 3 2 ...
$ age : num 22 38 26 35 35 NA 54 2 27 14 ...
# Column title is equal to "Master" and Column age is NA
> cleantrain %>% filter(Title == "Master" & is.na(age))
train$PassengerId survived Title fare sbsp parch alone familysize age
1 66 1 Master 15.2458 1 1 0 3 NA
2 160 0 Master 69.5500 8 2 0 11 NA
3 177 0 Master 25.4667 3 1 0 5 NA
4 710 1 Master 15.2458 1 1 0 3 NA
我只需要用8替换这些NA。使用以下突变不会更新原始cleantrain数据。帧
>cleantrain %>% filter(Title == "Master" & is.na(age)) %>% mutate(age = 8) #will put the right info on the right place.
train$PassengerId survived Title fare sbsp parch alone familysize age
1 66 1 Master 15.2458 1 1 0 3 8
2 160 0 Master 69.5500 8 2 0 11 8
3 177 0 Master 25.4667 3 1 0 5 8
4 710 1 Master 15.2458 1 1 0 3 8
#but not actually. when checking dataframe values remains NAS
>cleantrain %>% filter(Title == "Master" & is.na(age))
train$PassengerId survived Title fare sbsp parch alone familysize age
1 66 1 Master 15.2458 1 1 0 3 NA
2 160 0 Master 69.5500 8 2 0 11 NA
3 177 0 Master 25.4667 3 1 0 5 NA
4 710 1 Master 15.2458 1 1 0 3 NA
我可以用变异吗？任何不需要/if循环的Dply/quick函数？#学习R
@akrun的replace解决方案将在您想要用固定值更新行的情况下工作。一般来说，你必须使用ifelse功能，我相信：
cleantrain <- cleantrain %>%
mutate(age = ifelse(Title == 'Master' & is.na(age),
8,
age))