[R] Plotting lm() attributes

[Prof Brian Ripley]

On Wed, 12 Nov 2003, Tony Plate wrote:

> I believe this is the sort of things that the functions resid() and 
> predict(), in conjunction with na.exclude, are designed for.  E.g.:
> 
>  > data <- data.frame(x=c(1:5), y=c(1,3,2,NA,4))
>  > m <- lm(y~x, data=data, na.action=na.exclude)
>  > predict(m)
>         1        2        3        4        5
> 1.400000 2.028571 2.657143       NA 3.914286
>  > resid(m)
>            1           2           3           4           5
> -0.40000000  0.97142857 -0.65714286          NA  0.08571429
>  >
> 
> Note that NA's are not reintroduced if na.action=na.omit, which is the 
> default (unless you have options("na.action") set otherwise).  Also, note 
> that this technique produces a NA fitted value where a non-NA one could be 
> produced (use predict(m, newdata=data) to get those values.)

More accurately, where a non-NA prediction could be produced.  There never 
was a fitted value for those cases, so NA is correct.  That predict gives 
what people expect with NA values is a new feature in 1.8.0.

And please, please, folks use the extractor functions and not the
components (NOT attributes) directly.

> 
> hope this helps,
> 
> Tony Plate
> 
> At Thursday 11:40 AM 11/13/2003 +1300, Murray Jorgensen wrote:
> >Suppose you fit a linear model
> >
> > > model.1 ~ lm(v1 ~ ..., data=myframe)
> >
> >and v2 is some other column of myframe typically not in the model. You 
> >will often want to try
> >
> > > plot(v2, model.1$residuals)
> >
> >but this will fail if there are NAs in the response v1 as 
> >model.1$residuals has length equal to the number of nonmissing values 
> >in  v1. I suppose
> >
> > > plot(v2[!is.na(v1)], model.1$residuals)
> >
> >does the job, but it seems irritating that model.1$residuals, does not 
> >have length agreeing with the number of rows in the data frame. It would 
> >be even more irritating for model.1$fitted.values, where the removed 
> >elements would often have nonmissing values.
> >
> >Murray
> >
> >--
> >Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
> >Department of Statistics, University of Waikato, Hamilton, New Zealand
> >Email: maj at waikato.ac.nz                                Fax 7 838 4155
> >Phone  +64 7 838 4773 wk    +64 7 849 6486 home    Mobile 021 1395 862
> >
> >______________________________________________
> >R-help at stat.math.ethz.ch mailing list
> >https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> 
> Tony Plate   tplate at acm.org
> 
> ______________________________________________
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> 
> 

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595