[R] how to "vectorize" this?

[markleeds at verizon.net]

Hi:  if i understand, i think

newx<-x[ x %in% key]

should give you what you want.



On Sun, Jan 25, 2009 at 10:27 PM, Akshaya Jha wrote:

> Hi,
>
> I have the following datasets:
> x=data I am looking through
> key=a set of data with the codes I want
>
> I have the following issue:
> I want the subset of x which has a code contained in the key dataset. 
> That is, if x[i] is contained in the key dataset, I want to keep it. 
> Note that x may contain multiple of the same codes (or obviously none 
> of that code as well)
>
> I currently use two for-loops thusly in my R-code:
>
> k=1
> y=data.frame(1,stringsAsFactors=FALSE)
> for(i in 1:length(x)){
> for(j in 1:length(key)){
>
> if(x[i]==key[j]){
> y[k]=x[i]
> k=k+1;
> }
>
> }
> }
>       However, my dataset (x in this example) is pretty large, so I 
> want to avoid using two for-loops.  Does anybody know an easier way to 
> approach this?
>
> Thanks
>
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