Home/ Questions/Q 1661
Answered
Max
Asked: 2022-04-26T11:41:26+00:00

Rolling paste strings across columns

I have this type of data:

df <- data.frame(
  w1 = c("A", "B", "C", "E", "F", "G"),
  w2 = c("B", "G", "C", "D", "E", "V"),
  w3 = c("D", "S", "O", "F", NA, "N"),
  w4 = c("E", "U", NA, "T", NA, NA),
  w5 = c("C", NA, NA, NA, NA, NA)
)

I need to iterate through column pairs to rolling-paste the separate strings into bigrams. Note that in the actual data the strings are of variable character length and character type. I’ve tried this but it fails:

df[, paste0("bigr_", 1:4, "_", 2:5)] <- lapply(df[, 1:5], 
                                               function(x) paste(x[i], x[i+1], sep = " "))

The expected output is:

  w1 w2   w3   w4   w5 bigr_1_2 bigr_2_3 bigr_3_4 bigr_4_5
1  A  B    D    E    C      A B      B D      D E      E C
2  B  G    S    U <NA>      B G      G S      S U     <NA>
3  C  C    O <NA> <NA>      C C      C O     <NA>     <NA>
4  E  D    F    T <NA>      E D      D F      F T     <NA>
5  F  E <NA> <NA> <NA>      F E     <NA>     <NA>     <NA>
6  G  V    N <NA> <NA>      G V      V N     <NA>     <NA>

I’d be most interested in a dplyr solution but am open and grateful for other solutions as well.

r
Share

1 Answer

  1. Best Answer
    df <- data.frame(
  w1 = c("A", "B", "C", "E", "F", "G"),
  w2 = c("B", "G", "C", "D", "E", "V"),
  w3 = c("D", "S", "O", "F", NA, "N"),
  w4 = c("E", "U", NA, "T", NA, NA),
  w5 = c("C", NA, NA, NA, NA, NA)
)

library(tidyverse)
df %>% 
  mutate(rn = row_number()) %>% 
  pivot_longer(-rn, values_drop_na = TRUE) %>% 
  group_by(rn) %>% 
  mutate(bigr = paste0(value, "_", lead(value))) %>% 
  mutate(bigr = if_else(str_detect(bigr, "_NA"), NA_character_, bigr)) %>% 
  pivot_wider(rn, names_from = c(name), values_from = c(value, bigr)) %>% 
  ungroup()
#> # A tibble: 6 × 11
#>      rn value_w1 value_w2 value_w3 value_w4 value_w5 bigr_w1 bigr_w2 bigr_w3
#>   <int> <chr>    <chr>    <chr>    <chr>    <chr>    <chr>   <chr>   <chr>  
#> 1     1 A        B        D        E        C        A_B     B_D     D_E    
#> 2     2 B        G        S        U        <NA>     B_G     G_S     S_U    
#> 3     3 C        C        O        <NA>     <NA>     C_C     C_O     <NA>   
#> 4     4 E        D        F        T        <NA>     E_D     D_F     F_T    
#> 5     5 F        E        <NA>     <NA>     <NA>     F_E     <NA>    <NA>   
#> 6     6 G        V        N        <NA>     <NA>     G_V     V_N     <NA>   
#> # … with 2 more variables: bigr_w4 <chr>, bigr_w5 <chr>

    Created on 2022-04-26 by the reprex package (v2.0.1)

    • 0

Leave an answer

You must login to add an answer.

Need An Account,