Select rows up to certain value in R

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I have the following dataframe:

df1 <- data.frame(ID = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2),
                  var1 = c(0, 2, 3, 4, 2, 5, 6, 10, 11, 0, 1, 2, 1, 5, 7, 10))

I want to select only the rows containing values up to 5, once 5 is reached I want it to go to the next ID and select only values up to 5 for that group so that the final result would look like this:

ID      var1
1        0
1        2
1        3
1        4
1        2
1        5
2        0
2        1
2        2
2        1
2        5

I would like to try something with dplyr as it is what I am most familiar with.

group-by dplyr select r
1 Answers

You could use which.max() to find the first occurrence of var1 >= 5, and then extract those rows whose row numbers are before it.

library(dplyr)

df1 %>%
  group_by(ID) %>%
  filter(row_number() <= which.max(var1 >= 5)) %>%
  ungroup()

or

df1 %>%
  group_by(ID) %>%
  slice(1:which.max(var1 >= 5)) %>%
  ungroup()

# # A tibble: 11 × 2
#       ID  var1
#    <dbl> <dbl>
#  1     1     0
#  2     1     2
#  3     1     3
#  4     1     4
#  5     1     2
#  6     1     5
#  7     2     0
#  8     2     1
#  9     2     2
# 10     2     1
# 11     2     5
Darren Tsai0
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