[R] linear regression in a ragged array

[Greg Snow]

In general when you want to split up your data and do the same thing on each piece then combine the results back together it is good to look at the plyr package.  But for this specific case you should look at the lmList function in the nlme package which may do exactly what you want with the least effort.

-- 
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 Marcel Curlin
> Sent: Monday, March 21, 2011 3:26 AM
> To: r-help at r-project.org
> Subject: [R] linear regression in a ragged array
> 
> Hello,
> I have a large dataset of the form
> 
> subj   var1   var2
> 001    100    200
> 001    120    226
> 001    130    238
> 001    140    245
> 001    150    300
> 002    110    205
> 002    125    209
> 003    101    233
> 003    115    254
> 
> I would like to perform linear regression of var2 on var1 for each
> subject
> separately. It seems like I should be able to use the tapply function
> as you
> do for simple operations (like finding a mean of var1 for each
> subject), but
> I am not sure of the correct syntax for this. Is there a way to do
> this?
> 
> Many thanks, Marcel
> 
> --
> View this message in context: http://r.789695.n4.nabble.com/linear-
> regression-in-a-ragged-array-tp3393033p3393033.html
> Sent from the R help mailing list archive at Nabble.com.
> 
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