[R] Behavior of seq with vector from

[Bert Gunter]

##Is this what you mean ??

do.call(rbind,lapply(yourlist,"[",,seq(from=1,by=3,length=4)))

## note the ",," that omits the row argument in the call to "["

-- Bert Gunter
Genentech Nonclinical Biostatistics

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Rowe, Brian Lee Yung (Portfolio Analytics)
Sent: Friday, May 22, 2009 8:02 AM
To: Peter Dalgaard
Cc: r-help at r-project.org
Subject: Re: [R] Behavior of seq with vector from

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
 (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907


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