Get a list of companies with multiple share classes-CodePudding

I am a beginner in R, and I have a table that consists of two columns. The first column is the company name. The second one is the share class. Most of the time, companies have one class of shares. But I want get a list of companies with multiple share classes (say, two share classes).

Given this table

in this case, I want to get
Result

Thank you very much!

CodePudding user response：

You could do:

names(which(rowSums(table(df))>1))
[1] "3" "6"  # Companies 3 and 6 have more than 1 share class

or even

subset(aggregate(.~company, unique(df), length), `share class`>1)

  company share class
3       3           2
5       6           2

df <- structure(list(company = c(1L, 2L, 3L, 3L, 4L, 6L, 6L), `share class` = c("a", 
"a", "a", "b", "a", "a", "b")), class = "data.frame", row.names = c(NA, 
-7L))