how to create variables based on regex matches?

[von_olaf]

Consider this simple example

mytib <- tibble(mytext = c('hello world',
                           'nice computer'))

> mytib %>% mutate(myregex1 = str_detect(mytext, 'hello'),
+                  myregex2 = str_detect(mytext, 'nice'))
# A tibble: 2 x 3
  mytext        myregex1 myregex2
  <chr>         <lgl>    <lgl>   
1 hello world   TRUE     FALSE   
2 nice computer FALSE    TRUE 

Essentially, I would like to automate this variable creation and I am not sure what is the most efficient way to do so. The problem is that in my real dataset, I have many regexes I need to use that are stored in a list(myregex1 = 'hello', myregex2 = 'nice')
so creating a mutate for each of them is not good. Is purrr the solution?

Any ideas? Thanks!!

[cderv]

You can achieve that using tidyeval and !!!

library(tidyverse)

mytib <- tibble(mytext = c('hello world',
                           'nice computer'))

# your regex list
regex <- list(myregex1 = "hello",
              myregex2 = "nice")

# build the expressions for inside mutate
vars <- map(regex, ~ quo(str_detect(mytext, !!.x)))

# splice the vars list
mytib %>% 
  mutate(!!!vars)
#> # A tibble: 2 x 3
#>   mytext        myregex1 myregex2
#>   <chr>         <lgl>    <lgl>   
#> 1 hello world   TRUE     FALSE   
#> 2 nice computer FALSE    TRUE

^{Created on 2019-02-18 by the reprex package (v0.2.1)}

[von_olaf]

thanks that is really neat. Could you please just explain what the !!! is doing here? I was aware of the quo() and !! but I dont quite understand why your code works here... Why do the variables get the right name? thanks!

[mara]

!!! is the "unquote splice" operator

The !!! operator unquotes and splices its argument. The argument should represent a list or a vector. Each element will be embedded in the surrounding call, i.e. each element is inserted as an argument. If the vector is named, the names are used as argument names.

https://rlang.r-lib.org/reference/quasiquotation.html

[von_olaf]

thanks Mara! although I have to admit all these esoteric !! and !!! are sometimes a bit confusing to me. is there a good tutorial where I can get the big picture view of the tidyeval?

[mara]

Still a work in progress, but (it also has links to shorter resources in there):

Tidy evaluation