[tech-spec] Re: loop return vector
- From: Dirk Eddelbuettel <edd@xxxxxxxxxx>
- To: tech-spec@xxxxxxxxxxxxx
- Date: Sun, 27 Feb 2005 17:19:24 -0600
On 27 February 2005 at 12:44, James Sogi wrote:
|
| Kudos to Tim. Good stuff.
Yup. Nice work. We could do with more of that on here ...
| Requesting help on ?"for" loop question (R 2.0 on XP), please.
|
| for(i in 1:5) a <- (i > 2)
| > a
| [1] TRUE
| > print(a)
| [1] TRUE
|
| #how do I get it to return entire vector, not just 1? What am I missing
| here?
You are assigning to a scalar, so it becomes a scalar. Alternatives:
i) Vectorised assignmentL
> i <- 1:5
> a <- (i>2)
> a
[1] FALSE FALSE TRUE TRUE TRUE
ii) Assign to vector elements inside the loop, but note that you need to
*have* a suitable a before you can assign to a[i]:
> rm(a)
> a <- vector(length=5, mode="integer")
> for (i in 1:5) a[i] <- (i>2)
> a
[1] 0 0 1 1 1
> rm(a)
> a <- vector(length=5, mode="logical")
> for (i in 1:5) a[i] <- (i>2)
> a
[1] FALSE FALSE TRUE TRUE TRUE
Hth, Dirk
--
Better to have an approximate answer to the right question than a precise
answer to the wrong question. -- John Tukey as quoted by John Chambers
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