[R] R hang-up using lm

[Raubertas, Richard]

Within the last few weeks, someone else reported a similar
problem when using the results of tapply in a call to rlm().
Note that the result of tapply is a 1D array, and it appears
there is a general problem with using such a thing on the
RHS in formula-based modeling functions:

set.seed(3)
yy <- rnorm(20)
gg <- rep(1:10, 2)
y <- tapply(yy, gg, median)
x <- 1:10
z <- lm(y ~ x)  # OK
z <- lm(x ~ y)  # crashes R

(R 1.8.1 on Windows XP Pro)

Rich Raubertas
Merck & Co.

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Jonathan Williams
> Sent: Tuesday, April 27, 2004 1:17 PM
> To: Ethz. Ch
> Subject: [R] R hang-up using lm
> 
> 
> Dear R-helpers,
> I have found a slightly annoying problem when trying to
> plot lines on graphs. I first created my data using
> tapply, thus:-
> y1=as.vector(fit1$coef$random$id)
> x1=tapply(o1,id,median,na.rm=T)
> x2=tapply(o2,id,median,na.rm=T)
> 
> #then I plot the data, thus:-
> plot(x1[x2==0],y[x2==0])
> #if I now try to fit the linear regression, R 'hangs up'
> abline(lm(y[x2==0]~x1[x2==0]),lty='solid')
> #but, curiously, the problem does not occur if I plot the lowess line
> lines(lowess(y[x2==0]~x1[x2==0]))
> 
> I can also avoid the problem by coercing x1 and x2 to be vectors.
> So, I don't need help to solve the problem. But, it seems an odd
> problem since it affects one plotting method, but not the other, 
> and it actually causes R to crash.
> 
> Jonathan Williams
> OPTIMA
> Radcliffe Infirmary
> Woodstock Road
> OXFORD OX2 6HE
> Tel +1865 (2)24356
> 
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