These are the 2 example data frames
s1=data.frame(id=c(1,2,3,4),sex=c("M","M,","F","F"))
s2=data.frame(id=c(1,1,2,2,2,3,4),symp=c("cold","fever","headache","pain","cough","sneeze","cramps"))
I want to combine this in such a way that it looks like
s3=data.frame(id=c(1,2,3,4),sex=c("M","M,","F","F"), symp=c("cold,fever","headache,pain,cough","sneeze","cramps"))