On Mon, 24 Oct 2011, Dennis Murphy wrote: > xyplot('TDS'$quant ~ 'Cond'$quant | burns.tds.anal$site ) Dennis, xyplot('TDS'$quant ~ 'Cond'$quant | burns.tds.anal$site) Error in "TDS"$quant : $ operator is invalid for atomic vectors I tried that earlier today. Rich