Create Function

General
2

Using some tidyverse tools,

library(dplyr)
library(tidyr)
library(lubridate)

df <- tibble(
 demo = c("73C23", "62R31", "62M26", "58C44", "53R02", NA, "78R58", "76C63") 
)
df <- df %>% 
  separate(
    col = demo, 
    into = c("birth_year", "birth_month_index", "other"),
    sep = c(2,3)
  ) %>% 
  mutate(
    birth_year = as.numeric(birth_year),
    birth_year = case_when(
      birth_year > 18 ~  (1900 + birth_year),
      birth_year <= 18 ~ (2000 + birth_year),
      TRUE ~ birth_year
    )
  )

df
#> # A tibble: 8 x 3
#>   birth_year birth_month_index other
#>        <dbl> <chr>             <chr>
#> 1       1973 C                 23   
#> 2       1962 R                 31   
#> 3       1962 M                 26   
#> 4       1958 C                 44   
#> 5       1953 R                 02   
#> 6         NA <NA>              <NA> 
#> 7       1978 R                 58   
#> 8       1976 C                 63
  • Note separate for splitting your single variable into it's parts
  • case_when and mutate for reworking the three new columns.

Here's a nice cheatsheet on these tasks:

With your birth_month, I personally like to merge over your index.
The month indices you're working with is not totally clear to me, but I hope you get the idea



Months <- tibble(
  month_index = LETTERS[1:12], 
  month = lubridate::month(1:12, label = TRUE)
)

df <- df %>% 
  left_join(
    Months,
    by = c('birth_month_index' = 'month_index')
)
df
#> # A tibble: 8 x 4
#>   birth_year birth_month_index other month
#>        <dbl> <chr>             <chr> <ord>
#> 1       1973 C                 23    Mar  
#> 2       1962 R                 31    <NA> 
#> 3       1962 M                 26    <NA> 
#> 4       1958 C                 44    Mar  
#> 5       1953 R                 02    <NA> 
#> 6         NA <NA>              <NA>  <NA> 
#> 7       1978 R                 58    <NA> 
#> 8       1976 C                 63    Mar

Created on 2018-10-31 by the reprex package (v0.2.1)

A good way to ask a quest like this is with a reproducible example, or what folks call a reprex for short. REPRoducible EXample (reprex)? A reprex makes it much easier for others to understand your issue and figure out how to help.

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