r - assign col value to first, second,third value observed in different column

Question

I have a df with patient ids and a binary indicator for whether they have experienced an intervention or not. I want to make a new column called "time_post" which tells me how many timepoints have passed since experiencing the intervention.

here is my DF:

names<-c("tom","tom","tom","tom","tom","tom","tom","tom", "john", "john","john", "john","john", "john","john", "john")
post<-as.numeric(0,0,0,1,1,1,1,1,0,1,1,1,1,1,1,1)
df<-data.frame(names,post)

this is what I have tried:

df$time_post<-ifelse(df$post==1[1],1,0)   ##this tries to assign 1 to "time_post" for first value of 1 seen in post

df$time_post<-ifelse(df$post==1[2],2,df$time_post)  ##trying to apply same logic here, but doesn't work. Introduces NAs into time_post column.

This is my desired output;

names post time_post
1    tom    0         0
2    tom    0         0
3    tom    0         0
4    tom    1         1
5    tom    1         2
6    tom    1         3
7    tom    1         4
8    tom    1         5
9   john    0         0
10  john    1         1
11  john    1         2
12  john    1         3
13  john    1         4
14  john    1         5
15  john    1         6
16  john    1         7

Thank you in advance

Answer 1

尝试这个：

df<-data.frame(names=c("tom","tom","tom","tom","tom","tom","tom","tom",
                       "john", "john","john", "john","john", "john","john", "john"),
               post=c(0,0,0,1,1,1,1,1,0,1,1,1,1,1,1,1))
df$time_post <- with(df, ave(post,names,FUN=cumsum))

这给了你：

> df
   names post time_post
1    tom    0         0
2    tom    0         0
3    tom    0         0
4    tom    1         1
5    tom    1         2
6    tom    1         3
7    tom    1         4
8    tom    1         5
9   john    0         0
10  john    1         1
11  john    1         2
12  john    1         3
13  john    1         4
14  john    1         5
15  john    1         6
16  john    1         7