[R] Formula that includes previous row values

[Pele]

Hi Greg - this is perfect - Thank You!

Also, thanks to everyone for the other suggestions



Greg Snow-2 wrote:
> 
> How about:
> 
> x3 <- cumsum( x2* 0.24^(5:0) ) / 0.24^(5:0)
> 
> with the 5 replaced by the length -1 for the more general case.
> 
> -- 
> Gregory (Greg) L. Snow Ph.D.
> Statistical Data Center
> Intermountain Healthcare
> greg.snow at imail.org
> 801.408.8111
> 
> 
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
>> project.org] On Behalf Of Pele
>> Sent: Monday, February 23, 2009 1:59 PM
>> To: r-help at r-project.org
>> Subject: [R] Formula that includes previous row values
>> 
>> 
>> Hi R users,
>> 
>> Is there an easy way in R to generate the results table below using
>> table 1
>> and the formula (simplified version of the real problem)?  It would be
>> easy
>> if I knew the R equivalent of SAS's retain function, but could not find
>> one.
>> 
>> Thanks in Advance for any help!
>> 
>> table1:
>> 
>> ID	X2	   X3
>> 1.00	1.00	   0
>> 2.00	0.00
>> 3.00	1.00
>> 4.00	3058
>> 5.00	0.00
>> 6.00	6.00
>> 
>> Formula: X3 = x2 + (.24 * x3)
>> 
>> where the values in the x3 column of the result table are retained from
>> previous x3 rows.. Also the first x3 value is initialized to 0 to start
>> 
>> e.g.
>> 	for ID=1 we have  1 + .24(0) 		        = 1.00
>> 	for ID=2 we have  0 + .24(1) 		        = 0.24
>> 	for ID=3 we have  1 + .24(.24) 		= 1.06
>> 	for ID=4 we have  3058 + .24(1.06) 	= 3058.25
>>         etc.............
>> 
>> Results:
>> ID	X2	x3
>> 1.00	1.00	1.00
>> 2.00	0.00	0.24
>> 3.00	1.00	1.06
>> 4.00	3058 	3058.25
>> 5.00	0.00	733.98
>> 6.00	6.00	182.16
>> --
>> View this message in context: http://www.nabble.com/Formula-that-
>> includes-previous-row-values-tp22170010p22170010.html
>> Sent from the R help mailing list archive at Nabble.com.
>> 
>> ______________________________________________
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>> PLEASE do read the posting guide http://www.R-project.org/posting-
>> guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> 
> ______________________________________________
> R-help at 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.
> 
> 

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