Concatenating strings with multiple separators using paste() in R

Question

See the following reproducible example:

require(tidyverse)

set.seed(1)
reprex_df <- data.frame(
  var1 = sample(1:10),
  var2 = sample(11:20),
  var3 = sample(21:30)
)

I am trying to create a new column containing URLs created from concatenating the other variables from each row into a string with "https://www.google.com/search?q=", using the following code:

reprex_df %>% mutate(new_col = c(paste("https://www.google.com/search?q=", var1, var2, var3, sep="+")))

Which results in:

https://www.google.com/search?q=+3+13+30

The problem with this is that it puts a + between the https://www.google.com/search?q= and var1, which is not a valid format for the URL. I need no separator between these strings. Like so:

https://www.google.com/search?q=3+13+30

Can I somehow specify to use a different separator for this part of the conjunction using paste(), or do I have to take a totally different approach? Any ideas?

Answer 1

1. paste0 Perhaps the easiest way is to specify the + signs as arguments with paste0 rather than using sep:

   root <- "https://www.google.com/search?q="
   reprex_df %>% 
     mutate(new_col = paste0(root, var1, "+", var2, "+", var3))
   

2. sprintf sprintf is another possibility:

   fmt <- "https://www.google.com/search?q=%d+%d+%d"
   reprex_df %>%
     mutate(new_col = sprintf(fmt, var1, var2, var3))
   

3. sub Yet another possibility is to use the code in the question but follow it with code to remove the first +:

   root <- "https://www.google.com/search?q="
   reprex_df %>% 
     mutate(new_col = paste(root, var1, var2, var3, sep="+"),
            new_col = sub("\\+", "", new_col))
   

4. allow extra + Google ignores the + after the equal sign so another approach is to just allow the extra plus to exist.

   root <- "https://www.google.com/search?q="
   reprex_df %>% 
     mutate(new_col = paste(root, var1, var2, var3, sep="+"))
   

Answer 2

You need another paste

reprex_df %>%
  mutate(new_col = paste0(
    "https://www.google.com/search?q=",
    paste(var1, var2, var3, sep = "+")
  ))
#   var1 var2 var3                                  new_col
#1     3   13   30  https://www.google.com/search?q=3+13+30
#2     4   12   22  https://www.google.com/search?q=4+12+22
#3     5   16   26  https://www.google.com/search?q=5+16+26
# ...

---

If you don't want to type all the variable names var1 to varn try purrr::invoke, thanks to @thelatemail

reprex_df %>%
  mutate(new_col = paste0("https://www.google.com/search?q=", 
                          invoke(paste, ., sep = "+")
                          )
         )

Or in base R

url <- "https://www.google.com/search?q=" # optional
transform(reprex_df,
          new_col = paste0(url, do.call(paste, c(reprex_df, sep = "+"))))