[datatable-help] Stackoverflow thread comparing merge times

[Matthew Dowle]

Does anyone have time to see if this post uses data.table correctly :

http://stackoverflow.com/questions/4322219/whats-the-fastest-way-to-merge-join-data-frames-in-r

The  dt[, colMeans(cbind(x, y)), by="g1,g2"] bit looks wrong to me. Is
that why it takes 131 seconds vs 2.73 for sqldf ?  Shouldn't it be
dt[,list(mean(x),mean(y)),by="g1,g2"] ?

And also the y2= bit of dt1[dt2,list(x,y1,y2=dt2$y2)] looks odd.

Matthew