Re: [R] Vector-subsetting with ZERO - Is behavior changeable?
Thank you very much. Learned something again!
Joh
William Dunlap wrote:
You can use [1] on the output of FUN to ensure that
exactly one value (perhaps NA from numeric(0)[1]) is
returned. E.g.
index - 1
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-
index,0)][1]})
[1] 2 1 NA
I'll also put in a plug for vapply, which throws an
error if FUN does not return what you expect it to:
vapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-
index,0)]},
FUN.VALUE=numeric(1))
Error in vapply(list(c(1, 2, 3), c(1, 2), c(1)), function(x) { :
values must be length 1,
but FUN(X[[3]]) result is length 0
vapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-
index,0)][1]},
FUN.VALUE=numeric(1))
[1] 2 1 NA
For long input vectors vapply can save a fair bit of
memory and time over sapply.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org]
On Behalf Of Johannes Graumann
Sent: Wednesday, October 05, 2011 4:29 AM
To: r-h...@stat.math.ethz.ch
Subject: [R] Vector-subsetting with ZERO - Is behavior changeable?
Dear All,
I have trouble generizising some code.
index - 0
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-
index,0)]})
Will yield a wished for vector like so:
[1] 3 2 1
But in this case (trying to select te second to last element in each
vector of the list)
index - 1
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-
index,0)]})
I end up with
[[1]]
[1] 2
[[2]]
[1] 1
[[3]]
numeric(0)
I would (massively) prefer something like
[1] 2 1 NA
My current implementation looks like
index - 1
unlist(
sapply(
list(c(1,2,3),c(1,2),c(1)),
function(x){
value - x[max(length(x)-index,0)]
if(identical(value,numeric(0))){return(NA)} else {return(value)}
}
)
)
[1] 2 1 NA
Quite the inelegant eyesore.
Any hints on how to do this better?
Thanks, Joh
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html and provide commented,
minimal, self-contained, reproducible code.
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
[R] Vector-subsetting with ZERO - Is behavior changeable?
Dear All,
I have trouble generizising some code.
index - 0
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)]})
Will yield a wished for vector like so:
[1] 3 2 1
But in this case (trying to select te second to last element in each vector
of the list)
index - 1
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)]})
I end up with
[[1]]
[1] 2
[[2]]
[1] 1
[[3]]
numeric(0)
I would (massively) prefer something like
[1] 2 1 NA
My current implementation looks like
index - 1
unlist(
sapply(
list(c(1,2,3),c(1,2),c(1)),
function(x){
value - x[max(length(x)-index,0)]
if(identical(value,numeric(0))){return(NA)} else {return(value)}
}
)
)
[1] 2 1 NA
Quite the inelegant eyesore.
Any hints on how to do this better?
Thanks, Joh
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Vector-subsetting with ZERO - Is behavior changeable?
You can use [1] on the output of FUN to ensure that
exactly one value (perhaps NA from numeric(0)[1]) is
returned. E.g.
index - 1
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)][1]})
[1] 2 1 NA
I'll also put in a plug for vapply, which throws an
error if FUN does not return what you expect it to:
vapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)]},
FUN.VALUE=numeric(1))
Error in vapply(list(c(1, 2, 3), c(1, 2), c(1)), function(x) { :
values must be length 1,
but FUN(X[[3]]) result is length 0
vapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)][1]},
FUN.VALUE=numeric(1))
[1] 2 1 NA
For long input vectors vapply can save a fair bit of
memory and time over sapply.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
-Original Message-
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
Behalf Of Johannes
Graumann
Sent: Wednesday, October 05, 2011 4:29 AM
To: r-h...@stat.math.ethz.ch
Subject: [R] Vector-subsetting with ZERO - Is behavior changeable?
Dear All,
I have trouble generizising some code.
index - 0
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)]})
Will yield a wished for vector like so:
[1] 3 2 1
But in this case (trying to select te second to last element in each vector
of the list)
index - 1
sapply(list(c(1,2,3),c(1,2),c(1)),function(x){x[max(length(x)-index,0)]})
I end up with
[[1]]
[1] 2
[[2]]
[1] 1
[[3]]
numeric(0)
I would (massively) prefer something like
[1] 2 1 NA
My current implementation looks like
index - 1
unlist(
sapply(
list(c(1,2,3),c(1,2),c(1)),
function(x){
value - x[max(length(x)-index,0)]
if(identical(value,numeric(0))){return(NA)} else {return(value)}
}
)
)
[1] 2 1 NA
Quite the inelegant eyesore.
Any hints on how to do this better?
Thanks, Joh
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
