[R-SIG-Mac] Rolling average length issue

[David Winsemius]

On Nov 5, 2010, at 12:03 PM, Sandy Zelka wrote:

>
> Please help....I'm trying to calculate a 5-point rolling average and  
> I keep getting a length issue.
> My script is

Not a SIG-Mac issue.

>
> ma5<-function (x){
> y<-numeric(length(x-2)
> for(i in 2(length(x)-1)){

You seem to missing an operator between 2 and (, and I am guessing you  
meant to type "*" or ":") but it is not clear SINCE YOU HAVE NOT  
DESCRIBED THE PROBLEM WELL. (And you have not posted the exact error  
message either.)

Also check FAQ for description of problems related to the hierarchy of  
arithmetic operators in R (I don't actually remember a FAQ nubmber for  
this one but it is "frequently asked":
 > x <- 1:10
 > 2:length(x) -1
[1] 1 2 3 4 5 6 7 8 9


> y[i]]<-(x[i-3]+x[i-2]+x[i-1]+x[i]+x[i+1]))/5

So have you checked at the ends of your ranges to see if these indices  
are meaningful? What is length(x) and would it be meaningful to  
request x[2-1 -3]? What is x[-2]  (or perhaps x[1-3] ) , after all? Or  
x[length(x)


> }
> Y}
>
> I keep getting a replacement has length zero
> I’ve tried changing the (x-2) to -3 and -4 and still get the same  
> issue.

More likely that the extremes would raise "out of range" problems than  
the "interior" indices.

> I’m thinking that it should be -2 and that this issue is in the  
> third line – any ideas?

Better problem description, better punctuation,  and posting to rhelp.


-- 
David.
>
>
> Sandy Zelka, CPA, CAE, MBA, LB
> Accounting Professor
> (518) 469-8040
>
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David Winsemius, MD
West Hartford, CT