filter id in cluster according another variable in R

问题

I have a data with 100 patients and each patient has values from 7 days (1 to 7). How can I select only patients according another variable only in day 1?

df <- data.frame(id = c(1, 1, 1, 2, 2, 2),
         day = c(1, 2, 3, 1, 2, 3),
         RRT = c(0, 1, 0, 1, 0, 0))

I want select only id whom had RRT=0 at day = 1.

回答1:

When using dplyr:

library(dplyr)
df %>% 
  group_by(id) %>% 
  filter(day == 1 & RRT == 0) %>% 
  select(id)

or base R:

df[df$day == 1 & df$RRT ==0,"id"]

回答2:

You can use the subset function in base R:

subset(df,RRT==0&day==1)

if you only need the id column the you can select

with(df,id[RRT==0&day==1])

来源：https://stackoverflow.com/questions/47977120/filter-id-in-cluster-according-another-variable-in-r