How to pivot multiple times for different variables in one dataframe in R?

Solution 1:

Perhaps this helps

library(tidyr)
pivot_longer(df, cols = matches('^(begin|end)'), 
   names_to = c("timepoint", ".value"), 
        names_pattern = "(.*)\\.(\\w+)$", values_drop_na = TRUE)

data

df <- structure(list(childid = c("m1", "m2", "m3", NA, "m4"), begin.age = c(12, 
3, NA, 4, 5), end.age = c(14, 5, 6, NA, 7), begin.weight = c(1, 
3, NA, 4, 5), end.weight = c(4, 5, 7, NA, 8), phase = c(1, 2, 
3, 4, 5)), class = "data.frame", row.names = c(NA, -5L))

Solution 2:

Alternative approach: Similar to akrun's approach but using names_sep instead of names_pattern:

library(dplyr)
library(tidyr)

df %>% 
  pivot_longer(
    cols = -c(childid, phase),
    names_to = c("timepoint", ".value"), 
    names_sep = "\\.",
    values_drop_na = TRUE
  )

  childid phase timepoint   age weight
  <chr>   <dbl> <chr>     <dbl>  <dbl>
1 m1          1 begin        12      1
2 m1          1 end          14      4
3 m2          2 begin         3      3
4 m2          2 end           5      5
5 m3          3 end           6      7
6 m4          4 begin         4      4
7 m5          5 begin         5      5
8 m5          5 end           7      8