[R] code speed help,

[Paul DeBruicker]

I have the following piece of code that combines lists comprised of 
components of varying length into a list with components of constant 
length.  I have found 2 ways to do it, and the faster of the two is 
posted below along with sample results.  Do you have any suggestions on 
how to decrease the calculation time by modifying the code?


 > ####Function###########
 > replacement2.idx<-function(life=w.life,N=years,n=samples){
+
+ yrs<-rep(N,n)
+ ind<-yrs-life
+
+ x1<-mapply(rep,times=life,x=0)
+ x2<-mapply(rep,times=ind,x=1)
+
+ x3<-data.frame(c(x1[[1]],x2[[1]]))
+
+ for(i in 2:n) x3<-data.frame(x3, append(x1[[i]],x2[[i]]))
+
+ x3<-t(x3)
+ }
 >
 >
 >
 > ###Sample Output###
 > samples<-5
 > years<-10
 > w.life<-round(rnorm(samples,5,1),digits=0)
 >
 > system.time(abc<-replacement2.idx())
[1] 0.04 0.00 0.07 0.00 0.00
 >
 > abc
                          1 2 3 4 5 6 7 8 9 10
c.x1..1....x2..1...      0 0 0 0 0 0 1 1 1  1
append.x1..i....x2..i... 0 0 0 0 0 0 1 1 1  1
append.x1..i....x2..i... 0 0 0 0 0 0 1 1 1  1
append.x1..i....x2..i... 0 0 0 0 1 1 1 1 1  1
append.x1..i....x2..i... 0 0 0 0 0 1 1 1 1  1
 >
 >
 >
 > ###1000 samples####
 > samples<-1000
 > w.life<-round(rnorm(samples,5,.5),digits=0)
 > system.time(method2<-replacement2.idx())
[1] 12.79  0.00 14.04  0.00  0.00
 >
 >
 >
 > ###5000 samples####
 > samples<-5000
 > w.life<-round(rnorm(samples,5,.5),digits=0)
 > system.time(method2<-replacement2.idx())
[1] 544.82   0.00 593.98   0.00   0.00
 >