[R] basic question about lm summaries
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Fri Apr 23 09:00:45 CEST 1999
On Thu, 22 Apr 1999, andy bernat wrote:
> I'm very new to R and I'm having trouble doing something that should be
> very simple (so I'm probably missing something quite obvious). When I
> > lm(data$CRIME~data$INCOME+data$HOUSING)
> I get the correct coefficients. However, when I try to get anything
> else out of this I get a message about a missing argument, e.g.:
> > summary.lm(lm.d1<-lm(data$CRIME~data$INCOME+data$HOUSING))
> Error: Argument "n" is missing, with no default
> None of the documentation mentions this argument "n", though I notice
You need to find out where that error message is coming from, by
traceback(). The documentation for the function giving the error
probably mentions n.
I won't try to solve the problem (you need to send us an example to
reproduce), but I will try to help make using R easier.
-- use lm(CRIME ~ INCOME + HOUSING, data=data). That is easier to read
(it would be even easier without the capitals) and ensures that the
variables are searched for in `data', which I hope is a data frame (but
lists work too, I believe).
-- Don't ever call methods unless you mean to do something very unusual. Do
summary(lm(CRIME ~ INCOME + HOUSING, data=data))
-- Unless you really need them, avoid assignments as arguments. They are
hard to read and easy to miss when skimming code. In other words, use
lm.d1 <- lm(data$CRIME~data$INCOME+data$HOUSING)
-- Try the opposite convention, d1.lm. Names with a system name . something
are normally either methods or helper functions. And surely it is the
data that is important here, not lm.
-- Avoid names like `data'. One guess as to the root of your problem is
that another object named `data' (other than the one you meant) is
being found. Now, some analysis suggests that is unlikely, but if the
data frame had been called `UScrime' I would have had no analysis to do.
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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