Hi Michael,

Try

fit <- lm(ozone~garden, data = test)
summary(fit)

See ?lm for more details.

HTH,
Jorge.-


On Sat, Oct 20, 2012 at 8:26 AM, Michael Grant <> wrote:

> New installation seems to have behavior I cannot figure out.  Here is
> illustrative sequence where I load a small data set (test) from Crawley's
> files and try to run a simple linear model and get an error message.
>  Oddly, R reports that the variable 'test$ozone' is numeric while, after
> attaching test, the variable ozone is not numeric.  Can someone please
> help?  This behavior is occurring with multiple data sets loaded from
> outside R.  Thank you in advance.
> Michael Grant
>
>
> Example:
> > test
>    ozone garden
> 1      3      A
> 2      5      B
> 3      4      A
> 4      5      B
> 5      4      A
> 6      6      B
> 7      3      A
> 8      7      B
> 9      2      A
> 10     4      B
> 11     3      A
> 12     4      B
> 13     1      A
> 14     3      B
> 15     3      A
> 16     5      B
> 17     5      A
> 18     6      B
> 19     2      A
> 20     5      B
> > is.data.frame(test)
> [1] TRUE
> > is.numeric(test$ozone)
> [1] TRUE
> > is.factor(test$garden)
> [1] TRUE
> > lm(ozone~garden)
> Error in model.frame.default(formula = ozone ~ garden, drop.unused.levels
> = TRUE) :
>   invalid type (list) for variable 'ozone'
>
> > attach(test)
> > is.numeric(ozone)
> [1] FALSE
> > is.numeric(test$ozone)
> [1] TRUE
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]


