[R] How to group by then count?
Monnand
monnand at gmail.com
Sun Jan 4 10:02:55 CET 2015
Hi all,
I thought this was a very naive problem but I have not found any solution
which is idiomatic to R.
The problem is like this:
Assuming we have vector of strings:
x = c("1", "1", "2", "1", "5", "2")
We want to count number of appearance of each string. i.e. in vector x,
string "1" appears 3 times; "2" appears twice and "5" appears once. Then I
want to know which string is the majority. In this case, it is "1".
For imperative languages like C, C++ Java and python, I would use a hash
table to count each strings where keys are the strings and values are the
number of appearance. For functional languages like clojure, there're
higher order functions like group-by.
However, for R, I can hardly find a good solution to this simple problem. I
found a hash package, which implements hash table. However, installing a
package simple for a hash table is really annoying for me. I did find
aggregate and other functions which operates on data frames. But in my
case, it is a simple vector. Converting it to a data frame may be not
desirable. (Or is it?)
Could anyone suggest me an idiomatic way of doing such job in R? I would be
appreciate for your help!
-Monnand
[[alternative HTML version deleted]]
More information about the R-help
mailing list