Peter Malewski (p.malewski@tu-bs.de)
Thu, 16 Dec 1999 21:19:57 +0100
Dear Faheem
Faheem Mitha wrote:
> I have the following question, which is elementary but I am unable to
> answer.
> In a for(i=10) loop, I am trying to represent the 10 1-dimensional vectors
> l1, l2,... l10 by some expression that will run through these values.
> ie. soppose I want to add l1 + ... + l10
> I could go
>
> x <- 0
> for(i in 1:10){ x <- x+ l(i)}
"()" indictes that a function is called. You can use a expression like
(get(paste( ... ))
> Vec1 <- 1:10
> Vec1 <- 1:10
> Vec2 <- 1:10
> Vec3 <- 1:10
> x <- 2
> for(i in 1:3) print(x + get(paste("Vec",i,sep="")))
[1] 3 4 5 6 7 8 9 10 11 12
[1] 3 4 5 6 7 8 9 10 11 12
[1] 3 4 5 6 7 8 9 10 11 12
A better way might be a Data.frame / matrix representation:
> xx <- data.frame(Vec1,Vec2,Vec3)
> xx+x
Vec1 Vec2 Vec3
1 3 3 3
2 4 4 4
3 5 5 5
4 6 6 6
5 7 7 7
6 8 8 8
7 9 9 9
8 10 10 10
9 11 11 11
10 12 12 12
> This should return x to be the sum of the 10 li's for i from 1 to 10
> except of course I'm doing something more complicated.
> But l(i) of course does not serve to represent l1 etc? What should I do?
??? Perhaps this includes a useful idea:
> x + apply(xx , 2 , sum)
Vec1 Vec2 Vec3
57 57 57
or:
> apply(xx , 2 , function( yy )x + sum(yy))
Vec1 Vec2 Vec3
57 57 57
Hope this answer will help a bit
Peter
>
>
> Faheem Mitha,
>
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