How to extract the first time a non-zero number occurs in dataframe n R?-CodePudding

In an experiment, I'm trying to find the time to first birth. There are four animals as given by id and rep (A1, A2, B1, B2), their age and babies. For each id and rep, I want to only retain the rows where babies were first born

id <- c("A","A","A","A","A","A","B","B","B","B","B","B","B","B","B")
rep <- c(1,1,1,2,2,2,1,1,1,1,2,2,2,2,2)
age <- c(0,1,2,0,1,2,0,1,2,3,0,1,2,3,4)
babies <- c(0,0,1,0,1,0,0,0,0,1,0,0,0,1,1)

df <- data.frame(id,rep,age,babies)

So in here, the final dataframe should look like this

id <- c("A","A","B","B")
rep <- c(1,2,1,2)
age <- c(2,1,3,3)
babies <- c(1,1,1,1)

df <- data.frame(id,rep,age,babies)

CodePudding user response：

library(dplyr)
df %>% 
   group_by(id, rep) %>% 
   slice_max(babies, n = 1, with_ties = FALSE) %>%
    ungroup

df %>%
   group_by(id, rep) %>% 
   filter(row_number() == which(babies > 0)[1]) %>% 
   ungroup

CodePudding user response：

Here is one with arrange:

library(dplyr)

df %>% 
  group_by(id, rep) %>% 
  arrange(-babies, .by_group = TRUE) %>% 
  slice(1)

  id      rep   age babies
  <chr> <dbl> <dbl>  <dbl>
1 A         1     2      1
2 A         2     1      1
3 B         1     3      1
4 B         2     3      1