How to combine column values with delimiters as well as exceptions to delimiters?-CodePudding

I have the following data frame:

fruit <- c("apple", "orange", "peach", "")
color <- c("red", "orange", "", "purple")
taste <- c("sweet", "", "sweet", "neutral")

df <- data.frame(fruit, color, taste)

I want to add all the columns together into one column named "combined":

combined <- c("apple   red   sweet", "orange   orange", "peach   sweet", "purple   neutral")

And as a result, I have the following data frame:

df2 <- data.frame(fruit, color, taste, combined)

I took a stab at using regex:

df %>%
      unite("combined",
            fruit,
            color,
            taste,  
            sep="   ",
            remove = FALSE)

I've been trying to remove " " when it is in the beginning or in the end or if there's a blank preceding it using the following regex, but it feels sloppy and doesn't seem to achieve exactly what I want:

df %>%
  as_tibble() %>%
  mutate(across(any_of(combined), gsub, pattern = "^\\ |\\   \\   \\   \\ |\\   \\   \\ |\\   \\ |\\ $", replacement = "")) %>%
  mutate_if(is.character, trimws)

Any guidance would be appreciated! Thanks!

CodePudding user response：

We may replace the blanks ("") with NA and then use na.rm = TRUE in unite

library(dplyr)
library(tidyr)
df %>%
  mutate(across(everything(), ~ na_if(.x,  ""))) %>%
  unite(combined, everything(), sep = "   ", na.rm = TRUE, 
     remove = FALSE)

-output

            combined  fruit  color   taste
1 apple   red   sweet  apple    red   sweet
2     orange   orange orange orange    <NA>
3       peach   sweet  peach   <NA>   sweet
4    purple   neutral   <NA> purple neutral

CodePudding user response：

Create a function which takes two strings and produces their sum and apply it using Reduce .

library(dplyr)

Paste <- function(x, y) paste0(x, ifelse(x == "" | y == "", "", "   "), y)
df %>% mutate(combined = Reduce(Paste, .))

giving

   fruit  color   taste            combined
1  apple    red   sweet apple   red   sweet
2 orange orange             orange   orange
3  peach          sweet       peach   sweet
4        purple neutral    purple   neutral