How to preserve the order of a vector in a table in R?

问题

Pretty simple question, I assume. I am trying to do this for a different type of object (with class 'acf' and type 'list'), but I assume the answer is easily extendable for a vector (class numeric, type 'double'):

 x<-c(4, 5, 6, 1, 2, 10, 15)
 table(x)
 x
 1  2  4  5  6 10 15 
 1  1  1  1  1  1  1 

I would like the output of the table to be in the same order as the vector (4, 5, 6, 1, 2, 10, 15). How can I achieve this?

回答1:

 table(factor(x, levels=unique(x)))

来源：https://stackoverflow.com/questions/25960800/how-to-preserve-the-order-of-a-vector-in-a-table-in-r