Compute the number of distinct values in col2 for each distinct value in col1 in R

Question

I have a dataframe like this:

df <- data.frame(
          SchoolID=c(\"A\",\"A\",\"B\",\"B\",\"C\",\"D\"),
          Country=c(\"XX\",\"XX\",\"XX\",\"YY\"         


        

Answer 1

One approach, which does not rely on third-party libraries:

> as.data.frame(rowSums(table(df[!duplicated(df), ]), na.rm=T))
  rowSums(table(df[!duplicated(df), ]), na.rm = T)
A                                                1
B                                                2
C                                                1
D                                                1