[R] aggregate and list elements of variables in data.frame

[Eik Vettorazzi]

Hi,
if you are willing to use dplyr, you can do all in one line of code:

library(dplyr)
df<-data.frame(id=1:10,A=c(123,345,123,678,345,123,789,345,123,789))

df%>%group_by(unique_A=A)%>%summarise(list_id=paste(id,collapse=", "))->r

cheers


Am 06.06.2018 um 10:13 schrieb Massimo Bressan:
> #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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> 
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-- 
Eik Vettorazzi

Department of Medical Biometry and Epidemiology
University Medical Center Hamburg-Eppendorf

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