Question

I have a data frame A with name and type.

name    aa  tt  gg  cc  aa  at  ag  ac

 type    3   2   4   3   2   2   3   3

How can I create a new ranked data.frame B with type and a count of the number of times
the type occurred in data.frame A?

count   4   3   1   

type    3   2   4   

Thank you for your help.

Answer 1

One option is the table() function. For your data:

dat <- data.frame(name = c("aa","tt","gg","cc","aa","at","ag","ac"),
                  type = c(3,2,4,3,2,2,3,3))

it gives:

> (tab <- with(dat, table(type)))
type
2 3 4 
3 4 1

Now we just need to sort it:

> sort(tab, decreasing = TRUE)
type
3 2 4 
4 3 1

These steps can be combined, of course:

> with(dat, sort(table(type), decreasing = TRUE))
type
3 2 4 
4 3 1