Merging two columns with condition?

February 13, 2023

I have a dataframe that looks like this:

> dput(df)
structure(list(Ethnicity = c("Non-Hispanic/Non-Latino", 
"Non-Hispanic/Non-Latino", "Non-Hispanic/Non-Latino", NA, "Non-Hispanic/Non-Latino", 
"Non-Hispanic/Non-Latino", "Hispanic/Latino", "Non-Hispanic/Non-Latino", 
"Non-Hispanic/Non-Latino", NA), Race = structure(c(1L, 
1L, 1L, NA, 5L, 1L, 7L, 1L, 7L, NA), levels = c("White", "2+ Races", 
"American Indian or Alaska Native", "Asian", "Black or African American", 
"Native Hawaiian or Other Pacific Islander", "Other", "Refused/Unknown"
), class = "factor")), row.names = c(NA, -10L), class = c("data.table", 
"data.frame"), .internal.selfref = <pointer: 0x7fe0098120e0>, index = integer(0))

I want to combine the info in both the Ethnicity and Race columns, so that if an individual’s ethnicity is Hispanic/Latino, that is recorded in the Race column. If the individual is Non-Hispanic/Non-Latino, then that information does not need to be copied into the race column.

The dataframe should look like this:

> dput(r)
structure(list(Ethnicity = c("Non-Hispanic/Non-Latino", "Non-Hispanic/Non-Latino", 
"Non-Hispanic/Non-Latino", NA, "Non-Hispanic/Non-Latino", "Non-Hispanic/Non-Latino", 
"Hispanic/Latino", "Non-Hispanic/Non-Latino", "Non-Hispanic/Non-Latino", 
NA), Race = c("White ", "White", "White", NA, "Black or African American", 
"White", "Other (Hispanic/Latino)", "White", "Other", NA)), class = "data.frame", row.names = c(NA, 
-10L))

As you can see, row 7 includes that the individual was Hispanic/Latino in the Race column now.

>Solution :

As it is a data.table, we can use data.table methods – specify the i with a logical expression and paste to assign (:=) the value

library(data.table)
df[Ethnicity == "Hispanic/Latino", Race := sprintf("%s (%s)", Race, Ethnicity)]

-output

> df
                  Ethnicity                      Race
 1: Non-Hispanic/Non-Latino                     White
 2: Non-Hispanic/Non-Latino                     White
 3: Non-Hispanic/Non-Latino                     White
 4:                    <NA>                      <NA>
 5: Non-Hispanic/Non-Latino Black or African American
 6: Non-Hispanic/Non-Latino                     White
 7:         Hispanic/Latino   Other (Hispanic/Latino)
 8: Non-Hispanic/Non-Latino                     White
 9: Non-Hispanic/Non-Latino                     Other
10:                    <NA>                      <NA>