Re: [R] Group by a data frame with multiple columns

entical(datTest2,as.data.frame(dtTest2)) #[1] TRUE A.K. - Original Message - From: Michael Liaw To: r-help@r-project.org Cc: Sent: Saturday, August 3, 2013 8:11 PM Subject: [R] Group by a data frame with multiple columns Hi I'm trying to manipulate a data frame (that has about 10

[R] Group by a data frame with multiple columns

Hi I'm trying to manipulate a data frame (that has about 10 million rows) rows by "grouping" it with multiple columns. For example, say the data set looks like: Area Sex Year y Bob F 2011 1 Bob F 2011 2 Bob F 2012 3 Bob M 2012 3 Bob M 2012 2 Fred F 2011 1 Fr