R help - May 2013 - Function for finding matching values in two vectors.

Hi,
You could use:
which(a%in%b)
#[1] 1 2 3 4 5

a1<-c(1,2,5)

b1<-c(1,3,4,5,7)
which(a1%in%b1)
#[1] 1 3
A.K.



Hello! I created the following function for calculating which elements 
in vector a are existant in vector b. However, all I get is NA NA NA and I can?t
figure out why. =/



fun <- function(a, b) { 
? y <- rep(NA, length(a)) 
? x <- 0 
? while (x <= length(b)) { 
? ? x <- x + 1 
? ? for (i in 1:length(a)) { 
? ? ? ? y[i]<- (a[i] == b[x]) 
? ? } 
? } 
? return(y) 
} 

fun(a<-1:5,b<-1:9) 


Thanks for any help!

How about
?intersect
> a<-1:5;b<-1:9
> a
[1] 1 2 3 4 5
> b
[1] 1 2 3 4 5 6 7 8 9
> intersect(a, b)
[1] 1 2 3 4 5

I haven't used this in simulation, so I don't know how fast it is.
-Mike

On Tue, May 28, 2013 at 2:05 PM, arun <smartpink111 at yahoo.com>
wrote:
> Hi,
> You could use:
> which(a%in%b)
> #[1] 1 2 3 4 5
>
> a1<-c(1,2,5)
>
> b1<-c(1,3,4,5,7)
> which(a1%in%b1)
> #[1] 1 3
> A.K.
>
>
>
> Hello! I created the following function for calculating which elements
> in vector a are existant in vector b. However, all I get is NA NA NA and I
can?t figure out why. =/
>
>
>
> fun <- function(a, b) {
>   y <- rep(NA, length(a))
>   x <- 0
>   while (x <= length(b)) {
>     x <- x + 1
>     for (i in 1:length(a)) {
>         y[i]<- (a[i] == b[x])
>     }
>   }
>   return(y)
> }
>
> fun(a<-1:5,b<-1:9)
>
>
> Thanks for any help!
>
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