Hi Dimitri,
If I understood correctly, the following will do:
system.time(sum1 <- apply(mycombos, 1, function(x) sum(values1[x])))
system.time(sum2 <- apply(mycombos, 1, function(x) sum(values2[x])))
system.time(sum3 <- apply(mycombos, 1, function(x) sum(values3[x])))
cbind(sum1, sum2, sum3)
HTH,
Jorge.-
On Tue, Mar 26, 2013 at 8:12 AM, Dimitri Liakhovitski <> wrote:
> This is another method I can think of, but it's also slow:
>
> for(i in 1:nrow(mycombos)){ # i=1
> indexes=rep(0,10)
> myitems<-unlist(mycombos[i,1:4])
> indexes[myitems]<-1
> mycombos$sum1[i]<-sum(values1 * indexes)
> mycombos$sum2[i]<-sum(values2 * indexes)
> mycombos$sum3[i]<-sum(values3 * indexes)
> }
>
>
> On Mon, Mar 25, 2013 at 5:00 PM, Dimitri Liakhovitski <
> dimitri.liakhovit...@gmail.com> wrote:
>
> > Hello!
> >
> > # I have 3 vectors of values:
> > values1<-rnorm(10)
> > values2<-rnorm(10)
> > values3<-rnorm(10)
> > # In real life, all 3 vectors have a length of 25
> >
> > # I create all possible combinations of 4 based on 10 elements:
> > mycombos<-expand.grid(1:10,1:10,1:10,1:10)
> > dim(mycombos)
> > # Removing rows that contain pairs of identical values in any 2 of
> > these columns:
> > mycombos<-mycombos[!(mycombos$Var1 == mycombos$Var2),]
> > mycombos<-mycombos[!(mycombos$Var1 == mycombos$Var3),]
> > mycombos<-mycombos[!(mycombos$Var1 == mycombos$Var4),]
> > mycombos<-mycombos[!(mycombos$Var2 == mycombos$Var3),]
> > mycombos<-mycombos[!(mycombos$Var2 == mycombos$Var4),]
> > mycombos<-mycombos[!(mycombos$Var3 == mycombos$Var4),]
> > dim(mycombos)
> >
> > # I want to write sums of elements from values1, values2, and values 3
> > whose numbers are contained in each column of mycombos. Here is how I am
> > going it now - using a loop:
> > mycombos$sum1<-NA
> > mycombos$sum2<-NA
> > mycombos$sum3<-NA
> > for(i in 1:nrow(mycombos)){
> > mycombos$sum1[i]<-values1[[mycombos[i,"Var1"]]] +
> > values1[[mycombos[i,"Var2"]]] + values1[[mycombos[i,"Var3"]]] +
> > values1[[mycombos[i,"Var4"]]]
> > mycombos$sum2[i]<-values2[[mycombos[i,"Var1"]]] +
> > values2[[mycombos[i,"Var2"]]] + values2[[mycombos[i,"Var3"]]] +
> > values2[[mycombos[i,"Var4"]]]
> > mycombos$sum3[i]<-values3[[mycombos[i,"Var1"]]] +
> > values3[[mycombos[i,"Var2"]]] + values3[[mycombos[i,"Var3"]]] +
> > values3[[mycombos[i,"Var4"]]]
> > }
> > head(mycombos);tail(mycombos)
> >
> > # It's going to take me forever with this loop. Is there a faster way of
> > doing the dame thing? Thanks a lot!
> >
> > --
> > Dimitri Liakhovitski
> >
>
>
>
> --
> Dimitri Liakhovitski
>
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>
> ______________________________________________
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