Hi,
xl<- vector("list",7)
for(i in 5:7){##loop over numeric vector
xl[[i]] <- rnorm(i)
}
xl
#[[1]]
#NULL
#
#[[2]]
#NULL
#
#[[3]]
#NULL
#
#[[4]]
#NULL
#
#[[5]]
#[1] 0.3266762 0.4316069 1.2290551 -0.6725783 1.6159861
#
#[[6]]
#[1] -2.8560618 -0.5694743 -0.7325862 1.6786160 0.3883842 -0.3991854
#
#[[7]]
#[1] -1.22443607 0.66940158 0.97476608 -0.85964961 0.06331827 -0.40658831
#[7] 0.24824287
xlNew<- vector("list",4)
for(i in as.character(2:3)){##loop over character vector
xlNew[[as.numeric(i)]] <- rnorm(i)
}
xlNew
#[[1]]
#NULL
#
#[[2]]
#[1] -2.155804 1.780388
#
#[[3]]
#[1] 0.4192816 -1.0142512 -0.2125988
#
#[[4]]
#NULL
A.K.
----- Original Message -----
From: Liviu Andronic <landronim...@gmail.com>
To: "r-help@r-project.org Help" <r-help@r-project.org>
Cc:
Sent: Sunday, May 19, 2013 12:08 PM
Subject: [R] strange behaviour with loops and lists
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
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