[R] modifynig some elements of a vector

[jim holtman]

should be able to:

u <- unique(u)
x[u] <- x[u] + 1

On Thu, Feb 10, 2011 at 6:50 AM, Eric Elguero <Eric.Elguero at ird.fr> wrote:
> He everybody,
>
> I want to add 1 to some elements of  a vector:
>
> x is a vector
> u is a vector of idices, that is, integers
> assumed to be within the range 1..length(x)
> and I want to add 1 to the elements of x
> each time their index appears in u
>
> x[u]<-x[u]+1 works only when there are no
> duplicated values in u
>
> I found this solution:
>
> tu <- table(u)
> indices <- as.numeric(names(tu))
> x[indices] <- x[indices]+tu
>
> but it looks ugly to me and I would
> prefer to avoid calling the function 'table'
> since this is to be done millions of times
> as part of a simulation program.
>
> Eric Elguero
> Génétique & Adaptation des Plasmodium
> IRD
> Montpellier - FRance
>
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>



-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?