r - More elegant way of transforming data frames from wide to long data fromat by using reshape() or melt() -

i looking more elegant way of reshaping data frame using melt (reshape2) or reshape function.

let’s assume have simple data frame this:

d<-data.frame("pid"=factor(c(1,1,1,2,2,2)),               "cue1"=factor(c(1,2,3,1,2,3)),               "cue2"=factor(c(5,5,5,5,5,5))) 

and transform second , third columns single long one. code below works looking more elegant way:

d1<-data.frame("trigger"=as.vector(t(d[,c(2:3)]))) d1$pid<-factor(rep(c(1,2),each=6)) 

it important number of levels of 2 factors different (cue1 has 3, cue2 has 1 level). code above gives me new column looks (this want):

trigger 1 5 2 5 3 5 ... 

unfortunately, of examples on internet reshape discusses following (and in case, non-preferred) example:

trigger 1 2 3 1 2 3 ... 

but need former one.

thanks suggestions in advance.

if looking one-liner using melt, below approach (the order desired kept):

# assume df data frame df_new = data.frame(trigger = melt(t(df[,2:3]))[,3], pid = rep(df[,1], each=2)) df_new #    trigger pid # 1        1   1 # 2        5   1 # 3        2   1 # 4        5   1 # 5        3   1 # 6        5   1 # 7        1   2 # 8        5   2 # 9        2   2 # 10       5   2 # 11       3   2 # 12       5   2