[R] xyplot(): How to Apply Conditional?

[David Winsemius]

On Oct 17, 2012, at 1:29 PM, Rich Shepard wrote:

> On Wed, 17 Oct 2012, David Winsemius wrote:
>
>> What exactly is being requested? Do you just need to learn how to  
>> use the
>> subset parameter? I would not think that the conditioning syntax  
>> would be
>> used when there were only one level desired.
>
> David,
>
>  When I try
>
> xyplot(quant ~ sampdate | era, data = sb.d, main = 'Antimony  
> Concentrations
> by Time', ylab = 'Concentration (mg/L)', xlab = 'Time',
> subset=era('Pre-Mining'))
>
> this error is returned:
>
> Error in eval(expr, envir, enclos) : could not find function "era"
>
> But, 'era' is a factor in the data frame.
>
>  The syntax above works with bwplot() and I would like to understand  
> why
> it's not working with xyplot().

Furthermore, can you show "working" code that uses a column name as a  
function? That is the error being reported.

Perhaps if you changed to:

subset=era=='Pre-Mining'


-- 

David Winsemius, MD
Alameda, CA, USA