为数据框中列的每个值指定级别

Question

My question is simple but somehow I can`t figure it out.

I have an increasing numeric vector in which values are not unique.

a <- c(1,2,4,4,7,7,7,9,12,25,25,26)

I want to create another column b which will give me the corresponding level of each of the element of vector a. Here, b is:

b <- c(1,2,3,3,4,4,4,5,6,7,7,8)

Can someone please help me how do I achieve it?

Answer 1

This should do it:

as.integer(factor(a))

Or this is probably better:

match(a, unique(a))

Answer 2

use cumsum and diff ,hope it help,thanks.

b=cumsum(c(TRUE,diff(a)!=0))
 b
 [1] 1 2 3 3 4 4 4 5 6 7 7 8

Answer 3

Also,

findInterval(a, unique(a))
#[1] 1 2 3 3 4 4 4 5 6 7 7 8