On Sep 28, 2012, at 9:56 AM, Rich Shepard wrote:
> On Fri, 28 Sep 2012, David Winsemius wrote:
>
>> Wouldn't that involve specifying the 'subset' parameter (if bwplot accepts
>> a subset argument) or using the 'subset' function to pass the desired rows
>> to the data argument if it doesn't?
>
> David,
>
> That's what I tried:
>
>>> bwplot(quant ~ param | era, data=mg.d, main='Magnesium', ylab='Concentration
>>> (mg/L)', subset=era('Pre-mining'))
Sigh. If I were testing that strategy (which I did not try because you were too
busy to have included a working example) I would have written it:
bwplot(quant ~ param , data=mg.d, main='Magnesium', ylab='Concentration
(mg/L)', subset= era=='Pre-mining' )
That passes a logical vector which will "work" only if bwplot created an local
environment where column names of the 'data' argument have been added to the
local namespce. I do not know if that is true. I just looked at the bwplot help
page and do not see a subset argument documented there.
The other suggestion which it seems you were also to busy too have tried was:
bwplot(quant ~ param , main='Magnesium', ylab='Concentration
(mg/L)', data = subset( mg.dsubset, era=='Pre-mining' ) )
Wrapping a column name around a factor level with parentheses (which R takes to
mean there is a function named 'era' to be applied) and expecting R to
understand the you want a subset seems doomed to failure.
It makes no sense to me to condition on a factor that you know for certainty
has only one level in the data being offered.
--
David Winsemius, MD
Alameda, CA, USA
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