R function to recode variable

As Phil suggested, the data you want may already be curated in the {rworldmap} package. Here's some code to extract what it sounds like you're looking for.

library(tidyverse)

d <- rworldmap::countryExData[,2:4] %>% janitor::clean_names()

d %>% 
  filter(str_detect(epi_regions,pattern = "Middle")) %>% 
  mutate(continent = if_else(str_detect(geo_subregion, "Africa"), "Africa", "Middle East")) %>% 
  select(1, 4)
#>                             country   continent
#> 1              United Arab Emirates Middle East
#> 2                           Armenia Middle East
#> 3                            Cyprus Middle East
#> 4                           Algeria      Africa
#> 5                             Egypt      Africa
#> 6                              Iran Middle East
#> 7                              Iraq Middle East
#> 8                            Israel Middle East
#> 9                            Jordan Middle East
#> 10                           Kuwait Middle East
#> 11                          Lebanon Middle East
#> 12                          Morocco      Africa
#> 13                             Oman Middle East
#> 14                     Saudi Arabia Middle East
#> 15                            Sudan      Africa
#> 16                            Syria Middle East
#> 17                          Tunisia      Africa
#> 18                           Turkey Middle East
#> 19                            Yemen Middle East

^{Created on 2022-04-07 by the reprex package (v2.0.1)}

If you want to do this manually, you can use fct_collapse from package forcats, this is explained in this tutorial.

library(dplyr)
library(forcats)
dat %>%
  mutate(region = fct_collapse(country,
    MENA = c("Egypt", "Syria", "Lebanon")
  ))