[R] If loops

[John Fox]

Dear Laura, 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Laura Collins
> Sent: Sunday, October 03, 2004 8:32 AM
> To: R-help at stat.math.ethz.ch
> Subject: [R] If loops
> 
> Hi,
> 
>  
> 
> I'm a complete beginner to all this so I was hoping someone 
> could help me!
> 
>  
> 
> What I'm trying to do is to write a function that returns the 
> coordinates where a vector x is equal to a.  So say I invent 
> a vector x:
> 
> 
> x<-c(,5,8,9,8,3).
> 
> If a is a<-8.
> 
>  
> 
> I want the function to return the coordinates of x where the 
> number 8 appears (i.e. 2 4).
> 
> I know I need to set up an if loop but I'm really not sure 
> how to do this.
> 
>  
> 
> Any advice or clues will be much appreciated.
> 

> which(x == 8)
[1] 2 4

See ?which.

Note that your definition of x is in error (try it) and that <- in R means
assignment, not equality.

John