Filter only rows that contain exact two strings in a column

I have a data.frame as follow:

df = data.frame(sp_name = c("Xylopia brasiliensis", "Xylosma tweediana", "Zanthoxylum fagara subsp. lentiscifolium", "Schinus terebinthifolia var. raddiana", "Eugenia"), value = c(1, 2, 3, 4, 5))

Here’s the deal: I am only interested in subsetting/filtering the rows from the df that contain exactly two words (in my case, Xylopia brasiliensis and Xylosma tweediana). How can I proceed? I’m failing miserably in using the filter function from tidyverse

Thanks already.

>Solution :

We can use str_count to create a logical vector in filter

library(dplyr)
library(stringr)
df %>% 
    filter(str_count(sp_name, "\\w+") == 2)

-output

               sp_name value
1 Xylopia brasiliensis     1
2    Xylosma tweediana     2

Or this can be done with str_detect as well – match the word (\\w+) from the start (^) followed by a space and another word (\\w+) at the end ($) of the string

df %>%
    filter(str_detect(sp_name, "^\\w+ \\w+$"))

Or in base R with grep

subset(df, grepl("^\\w+ \\w+$", sp_name))
               sp_name value
1 Xylopia brasiliensis     1
2    Xylosma tweediana     2