R: Remove duplicates from a dataframe based on categories in a column

Question

Here is my example data set:

      Name Course Cateory
 1: Jason     ML      PT
 2: Jason     ML      DI
 3: Jason     ML      GT
 4: Jason     ML      SY
 5: Ja         


        

Answer 1

Here is a snippet that does what you asked:

df$Category <- factor(df$Category, levels = c("PT", "DI", "GT", "SY"))

df <- df[order(df$Category),]

df[!duplicated(df[,c('Name', 'Course')]),]

Output:

Name Course Category
Jason     ML       PT
Nancy     ML       PT
Jason     DS       DI
Nancy     DS       DI
John      DS       GT
James     ML       SY

Idea is that we sort based on the priority structure. Then we apply the unique operations, which will return the first match. The return will be what we want.