Select rows with common ids in grouped data frame

Question

I am searching for a simpler solution to the following problem. Here is my setup:

test <- tibble::tribble(
  ~group_name, ~id_name, ~varA, ~varB,
     \"g         


        

Answer 1

You can tabulate the the occurrence of id_name by group_name:

table(test$group_name,test$id_name)

If id_name is present in every group, we want columns that have all > 0 entris. We can simplify this logic using a combination of >0 and colMeans:

keep = names(which(colMeans(table(test$group_name,test$id_name)>0)==1))

Using this:

test[test$id_name %in% keep,]