#given the following reproducible and simplified example
t<-data.frame(id=1:10,A=c(123,345,123,678,345,123,789,345,123,789))
t
#I need to get the following result
r<-data.frame(unique_A=c(123, 345, 678,
789),list_id=c('1,3,6,9','2,5,8','4','7,10'))
r
# i.e. aggregate over the variable "A" and list all elements of the variable
"id" satisfying the criteria of having the same corrisponding value of "A"
#any help for that?
#so far I've just managed to "aggregate" and "count", like:
library(sqldf)
sqldf('select count(*) as count_id, A as unique_A from t group by A')
library(dplyr)
t%>%group_by(unique_A=A) %>% summarise(count_id = n())
# thank you
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