[R] restoring vector v from v[-i]

[Robin Hankin]

Hi

I have a little function that takes a vector v and an integer i.  I 
want to manipulate
v[-i] (to give v.new, say) and
then put (unmanipulated)  v[i] back into the appropriate place.  For 
example,


f <- function(v,i){
v.new <- v[-i]+10
return(c(v.new[1:(i-1)],v[i],v.new[i:length(v.new)]))
}

(my example is adding 10 to v[-i], but the real version is the solution 
of a complicated function involving
a  call to Solve(A,b))


Function f() works most of the time:
 > f(1:10,4)
  [1] 11 12 13  4 15 16 17 18 19 20
 > f(1:10,8)
  [1] 11 12 13 14 15 16 17  8 19 20


but fails at the "edges":

  f(1:10,1)
  [1] 12  1 12 13 14 15 16 17 18 19 20
 > f(1:10,10)
  [1] 11 12 13 14 15 16 17 18 19 10 NA 19
 >


[ I would want f(1:10,1) to start  1,12,13,...   and f(1:10,10) to end  
  . . . 18 19,10]


How best to get intended behaviour for i=1 and i=length(v)?




--
Robin Hankin
Uncertainty Analyst
Southampton Oceanography Centre
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743