[R] While loop working with TRUE/FALSE?

[Petr PIKAL]

Hi

> 
> Thanks to Berend and the others,
> 
> I've found a solution which works fine for my problem.
> 
> I have not only 2 vectors, but also 4.
> Question is, if q1 and q2 is equal to w1 and w2.
> The computational time is very short, also for large data.
> 
> q1 <- c(9,5,1,5)
> q2 <- c(9,2,1,5)
> 
> w1 <- c(9,4,4,4,5)
> w1 <- c(9,4,4,4,5)
> 
> v <- vector()
> for (i in 1:(length(q1))){
> v[i] <- any((q1[i] == w1) &  (q2[i] == w2))
> }

If i understand correctly you want to know if any value in q1 is also in 
w1 and q2 is in w2.
Therefore 
any((q2[2] == w2) & (q1[2] == w1))
is true in only if there is common elements in both vector pairs which is 
what 

> (q1 %in% w1) & (q2 %in% w2)
[1]  TRUE FALSE FALSE  TRUE

does.

For small vectors (several values) timing will be probably similar, 
however with moderate vectors with few thousand values there is 
considerable speedup.

> q1<-sample(q1, 10000, replace=T)
> q2<-sample(q2, 10000, replace=T)
> w1<-sample(w1, 100000, replace=T)
> w2<-sample(w2, 100000, replace=T)
> v2<- vector()
> system.time({
+ for (i in 1:(length(q1))){
+ v2[i] <- any((q1[i] == w1) &  (q2[i] == w2))
+ }})
   user  system elapsed 
  34.36    1.69   36.16 
> 
> system.time(v<-((q1 %in% w1) & (q2 %in% w2)))
   user  system elapsed 
   0.01    0.00    0.02 
> all.equal(v,v2)
[1] TRUE

Regards
Petr








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> 
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