[R] NA confusion (length question)

[Stratford, Jeffrey]

Josh, 

I am raising my cup of coffee to you - that worked perfectly.  

Cheers and thanks again! 

-----Original Message-----
From: Joshua Wiley [mailto:jwiley.psych at gmail.com] 
Sent: Tuesday, September 14, 2010 9:29 AM
To: Stratford, Jeffrey
Cc: r-help at r-project.org
Subject: Re: [R] NA confusion (length question)

Hi Jeffrey,

As a bit of a side note, data copied in html emails tends to show up
poorly (since emails to the list are converted to plain text).
Anyways, note the difference between:

length(mylm$residuals)
length(residuals(mylm))

Accessing the residuals value from mylm is *not* quite the same as
calling the residuals() function on mylm.  So, if you use:

cbind(residuals(mylm), mydata)

you should be good.

Hope that helps,

Josh

On Tue, Sep 14, 2010 at 6:20 AM, Stratford, Jeffrey
<jeffrey.stratford at wilkes.edu> wrote:
> Hi folks,
>
>
>
> I am running a very simple regression using
>
>
>
> mylm <- lm(mass ~ tarsus, na.action=na.exclude)
>
>
>
> I would like the use the residuals from this analysis for more
> regression but I'm running into a snag when I try
>
>
>
> cbind(mylm$residuals, mydata)  # where my data is the original data set
>
>
>
> The error tells me that it cannot use cbind because the length of
> mylm$residuals is 50 and mydata is 52.  This makes sense except I
> thought that na.exclude preserves length by inserting NA in residuals
> where there were NA's in the orginal data ( i = 3, 20).  When I ask to
> see the residuals( mylm$residuals) I see 52 numbers.  How can this be?
>
>
>
> I am just looking to see how I can produce a third vector with length =
> 52 and NA's for i=3,20.
>
>
>
> I'm using R 2.11.1 on Windows XP and the data are below
>
>
>
> Many thanks,
>
>
>
> Jeff
>
>
>
>
>
> tarsus
>
> mass
>
>
>
> 21.5
>
> 23.2
>
>
> 21.8
>
> 22.6
>
>
> 20.9
>
> NA
>
>
> 21.6
>
> 20.8
>
>
> 21.5
>
> 21.5
>
>
> 22
>
> 23.2
>
>
> 21.6
>
> 23
>
>
> 22.1
>
> 21
>
>
> 21.1
>
> 21
>
>
> 20.6
>
> 22.9
>
>
> 20.1
>
> 21.8
>
>
> 22.2
>
> 20.4
>
>
> 21.9
>
> 21.5
>
>
> 21.1
>
> 21.3
>
>
> 21.5
>
> 20.1
>
>
> 19.9
>
> 21.4
>
>
> 22.1
>
> 27.3
>
>
> 20.1
>
> 19.7
>
>
> 19.6
>
> 16.7
>
>
> 20.9
>
> NA
>
>
> 20.1
>
> 21.7
>
>
> 21.8
>
> 22.3
>
>
> 20.9
>
> 21.1
>
>
> 21.6
>
> 20.8
>
>
> 22.4
>
> 20.5
>
>
> 21.4
>
> 20.4
>
>
> 21.4
>
> 21
>
>
> 21.6
>
> 21
>
>
> 21.2
>
> 23.3
>
>
> 21.1
>
> 21.9
>
>
> 22
>
> 21
>
>
> 22.2
>
> 21.5
>
>
> 20.6
>
> 20.6
>
>
> 21.3
>
> 20.5
>
>
> 20.6
>
> 20.5
>
>
> 21.4
>
> 20.8
>
>
> 21.8
>
> 21.4
>
>
> 21.6
>
> 19.6
>
>
> 22.4
>
> 24.3
>
>
> 21.7
>
> 20.3
>
>
> 21.4
>
> 21.3
>
>
> 20.7
>
> 18.2
>
>
> 21.3
>
> 20.9
>
>
> 21.7
>
> 20.7
>
>
> 22.6
>
> 20
>
>
> 22
>
> 23
>
>
> 18.4
>
> 20
>
>
> 20.1
>
> 20.6
>
>
> 19.8
>
> 19.1
>
>
> 21.1
>
> 26.3
>
>
> 19.8
>
> 22.3
>
>
> 21.2
>
> 22.2
>
>
> 19.5
>
> 20.6
>
>
> 19.7
>
> 22.7
>
>
>
>
>
>
>
> ************************************
>
> Jeffrey A. Stratford
>
> Department of Health and Biological Sciences
>
> 84 W. South Street
>
> Wilkes University, PA 18766
>
> jeffrey.stratford at wilkes.edu
>
> 570-408-4761 (office)
>
> 570-332-2942 (cell)
>
> http://web.wilkes.edu/jeffrey.stratford/
>
> ************************************
>
>
>
>
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>
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>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/