combining mutate, ends_with, and if_else

[rvrgl]

Hi, I have a dataframe like the one below. I want to make a new column called "Species". I then want to populate that column with either "species1" or "species2", depending on the end of the sample ID (in the ID column). I have an example below of what I have tried, trying to use mutate, ends_with, and if_else, but I haven't figured out how to make it work yet.

library(dplyr)
library(tidyr)
library(stringr)

#make dataframe
ID<-c("ind1_species2","ind2_species2","ind1_species1","ind2_species2")
Year<-c(1999,1999,2000,2000)
df<-data.frame(ID,Year)
colnames(df)

#example of failed code
a<- df %>%
mutate(Species=ifelse(ends_with("species2")),"species2","species1")

[Yarnabrina]

Does it do what you want?

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
library(stringr)

df <- data.frame(ID = c("ind1_species2", "ind2_species2", "ind1_species1", "ind2_species2"),
                 Year = c(1999, 1999, 2000, 2000))
df %>%
    mutate(Species = str_extract(string = df[["ID"]],
                                 pattern = "(?<=_)(species[12])$"))
#>              ID Year  Species
#> 1 ind1_species2 1999 species2
#> 2 ind2_species2 1999 species2
#> 3 ind1_species1 2000 species1
#> 4 ind2_species2 2000 species2

^{Created on 2021-03-18 by the reprex package (v1.0.0)}

[rvrgl]

That works great. Thanks a lot for the quick response!

[rvrgl]

@Yarnabrina

df %>%
    mutate(Species = str_extract(string = df[["ID"]],
                                 pattern = "(?<=_)(species[12])$"))

Hi again,

I'm confused what the "[12]" means here. Just wondering if there is a quick explanation you could share?

Thanks!

[Yarnabrina]

Sure, no problem.

This regular expression will match either species1 or species2 at the end of a word followed by an underscore (_). What [12] means is either 1 or 2, and no other character.

You may find this site helpful to understand different regex you find online: https://regexr.com

[rvrgl]

Thanks so much, that is really helpful!