[R] strange behaviour with loops and lists

[Liviu Andronic]

Dear all,
I encountered this strange behaviour with loops and lists. Consider this:
xl <- list()
for(i in 5:7){##loop over numeric vector
    xl[[i]] <- rnorm(i)
}
> xl
[[1]]
NULL

[[2]]
[1] -0.4448192 -1.3395014

[[3]]
[1]  1.3214195 -1.2968560 -0.6327795


The above lists contained a NULL element for some reason. While the code below:
xl <- list()
for(i in as.character(2:3)){##loop over character vector
    xl[[i]] <- rnorm(i)
}
> xl
$`2`
[1] -1.139506  2.894280

$`3`
[1] 0.0599175 1.0793515 0.4296049


This resulting list contains no extraneous elements. Is this normal? Why?

Thanks,
Liviu

-- 
Do you know how to read?
http://www.alienetworks.com/srtest.cfm
http://goodies.xfce.org/projects/applications/xfce4-dict#speed-reader
Do you know how to write?
http://garbl.home.comcast.net/~garbl/stylemanual/e.htm#e-mail