Here is one way to approach this problem (there are lots of ways) #Convert to model matrix to account for factor variables iris <- model.matrix(~.-1,data=iris)
#Convert to data.table iris <- data.table(iris) candidates <- names(iris) #Setup interaction variables for every combination all.interactions <- as.data.table(t(combn(candidates,2))) all.interactions[ , interaction := paste(V1,V2,sep="__")] all.interactions[ , multiplier := paste(V1,V2,sep="*")] #Add interactions to data for (x in 1:nrow(all.interactions)) iris[ , paste0(all.interactions$interaction[x]) := eval(parse(text=all.interactions$multiplier[x]))] -- View this message in context: http://r.789695.n4.nabble.com/Extracting-specific-values-from-a-matrix-tp4695768p4695793.html Sent from the datatable-help mailing list archive at Nabble.com. _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
