[R] Behavior of seq with vector from

[Rowe, Brian Lee Yung (Portfolio Analytics)]

Brilliant! Thanks, Brian

-----Original Message-----
From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com] 
Sent: Friday, May 22, 2009 11:20 AM
To: Rowe, Brian Lee Yung (Portfolio Analytics)
Cc: Peter Dalgaard; r-help at r-project.org
Subject: Re: [R] Behavior of seq with vector from


Try it this way:

# test list of data frames
L <- list(anscombe[1:4], anscombe[5:8], anscombe[1:4], anscombe[5:8])

# get columns 2 and 3 from each component; cbind those together
do.call(cbind, lapply(L, "[", 2:3))


On Fri, May 22, 2009 at 11:01 AM, Rowe, Brian Lee Yung (Portfolio
Analytics) <B_Rowe at ml.com> wrote:
> So if I want to concatenate the output of multiple seq calls, there's no clear way to to do this?
>
> For background, I have a number of data.frames with the same structure in a list. I want to 'collapse' the list into a single data.frame but only keeping certain columns from each underlying data.frame. In my example below, I want to keep columns 2,3 in each underlying data.frame.
>
> I'm using do.call('cbind', my.list) and then using the statement below to extract only the columns I need (other details omitted for brevity). If there's a built-in or pre-built function to do this, I'm all eyes.
>
>
> Brian
>
> PS if this is unclear, flame away, and I'll post some code
>
> -----Original Message-----
> From: Peter Dalgaard [mailto:P.Dalgaard at biostat.ku.dk]
> Sent: Friday, May 22, 2009 6:20 AM
> To: Rowe, Brian Lee Yung (Portfolio Analytics)
> Cc: r-help at r-project.org
> Subject: Re: [R] Behavior of seq with vector from
>
>
> Rowe, Brian Lee Yung (Portfolio Analytics) wrote:
> ....
>> To get the value I want, I am using the following code:
>>> sort(as.vector(apply(array(c(2,3)), 1, seq, by=3,length.out=4)))
>> [1]  2  3  5  6  8  9 11 12
>>
>> So two questions:
>> 1. Is seq designed/intended to be used with a vector from argument, and
>> is this the desired behavior?
>> 2. If so, is there a cleaner way of implementing what I want?
>
> 1. Hmm, not really. NA.
>
> 2. I'd view it as an outer sum, stringed out to a single vector, hence:
>
>> c(outer(c(2,3), seq(0,,3,4), "+"))
> [1]  2  3  5  6  8  9 11 12
>
>
> --
>   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
>  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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