Good day, everyone
I'm new in using R and have learnt some useful tricks. I'm trying to get a count of number in column 'P_ID' and create a new column 'count' where I look at what number appears in P_ID and count same numbers in the same column and enter the retuned vaclue in the corresponding cell in 'count' column. I can do this in excel using the 'countif' function (e.g. =COUNTIF($A$2:$A$20,A2) ) and here are results:
P_ID Count
18 1
1 1
4 3
5 2
10 2
12 1
2 2
5 2
2 2
10 2
4 3
4 3
8 1
9 2
7 2
17 1
7 2
19 1
9 2
I've tried the following in R without getting the desired results:
library(dplyr)
dt<-tibble(P_ID=c(18,1,4,5,10,12,2,5,2,10,4,4,8,9,7,17,7,19,9))
dt%>%
mutate(count=for (x in 1:length(P_ID)) {sum(P_ID==P_ID)})%>%
View()
and only get:
P_ID
1 18
2 1
3 4
4 5
5 10
6 12
7 2
8 5
9 2
10 10
11 4
12 4
13 8
14 9
15 7
16 17
17 7
18 19
19 9
Showing 1 to 11 of 19 entries, 1 total columns
I'll appreciate it if somebody can advise me what to do and where I'm going wrong.
Thank you.