Sorry, sorry for taking your time. I solved the problem. data=transform(data,C= A+B) It is so simple. But if you dont know it is hard. Again sory for taking time -- View this message in context: http://r.789695.n4.nabble.com/adding-two-colmns-of-a-data-frame-tp3454556p3454572.html Sent from the R help mailing list archive at Nabble.com.