[R] Equivalent of SAS's FIRST. And LAST. Variable in R?

[Martyn Byng]

Hi,

I expect there are better ways of doing this then the following, but you
can probably get the same sort of thing using the split command

bb =
matrix(c(1,1,1,2,2,2,3,3,3,3,10,11,12,43,23,14,52,52,12,23),ncol=2,byrow
=FALSE)
aa = split(bb,bb[,1])
sapply(aa,function(temp) {cc = matrix(temp,ncol=ncol(bb));cc[nrow(cc),2]
- cc[1,2]})

where the first column of bb is the "ClientCode" the sapply gives the
difference in the second column of bb between the "last" and "first"
value for each client

Martyn
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Wang, Kevin (SYD)
Sent: 13 July 2010 07:52
To: r-help at r-project.org
Cc: Wang, Kevin (SYD); wang.kevin at gmail.com
Subject: [R] Equivalent of SAS's FIRST. And LAST. Variable in R?

Hi all,

I'm just wondering if there is a equivalent of SAS's FIRST. and LAST.
variables in R?

For example, suppose this is a snapshot of the data:
	  ClientCode CaseCode       open      close    Important
	1         37       28 2003-07-08 2003-09-02            1
	2         37      310 2003-11-01 2004-09-10            1
	3         37     1562 2007-04-03 2007-07-27            1
	4         38       29 2003-02-28 2007-09-05            1
	5         38      599 2004-07-14 2007-10-31            1

For each client, I want to see that if a case is important (Important =
1), then check its close date and the next open-date for the client.
E.g. for Client 37, I want to get the difference between Case 310's open
date and Case 28's close date, as well as find out whether Case 310 is
"Important".

I know how to get this using SAS's DATA step (with BY statement and
FIRST. variable).  But I'm having trouble finding the equivalent in R.

Any suggestions will be greatly appreciated!

Cheers,

Kevin


Kevin Wang
Senior Adviser, Government Advisory Services
Advisory

KPMG
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