R function to mutate 2 ID columns into two different rows/entries

Question

I have a data frame of events that have two columns for attendance IDs It looks like this.

event<-c(1:20)
name1<-c(101:120)
name2<-c(rep(NA,15),201:205)

df<-data.frame(event,name1,name2)

I want all the names in one column so I can join it to mult other data sets. It should look like this.

event<-c(1:16,16,17,17,18,18,19,19,20,20)
name<-c(101:116,201,117,202,118,203,119,204,120,205)

desired_df<-data.frame(event,name)

What is a good mutation/transformation to use for this process?

Answer 1

Using tidyr::pivot_longer():

library(tidyr)

desired_df <- df %>%
  pivot_longer(
    cols = c(name1, name2),
    values_drop_na = TRUE,
    names_to = NULL,
    values_to = "name")

print(desired_df, n = Inf)
# # A tibble: 25 × 2
#    event  name
#    <int> <int>
#  1     1   101
#  2     2   102
#  3     3   103
#  4     4   104
#  5     5   105
#  6     6   106
#  7     7   107
#  8     8   108
#  9     9   109
# 10    10   110
# 11    11   111
# 12    12   112
# 13    13   113
# 14    14   114
# 15    15   115
# 16    16   116
# 17    16   201
# 18    17   117
# 19    17   202
# 20    18   118
# 21    18   203
# 22    19   119
# 23    19   204
# 24    20   120
# 25    20   205