Syntax Help for xyplot()

Where's TDS? -- 'cause it's sure not in your data frame.

Bert,

summary(burns.tds.anal)
       site        sampdate           param         quant
  BC-3   :460   Min.   :1992-03-27   Ca  : 65   Min.   :   1.00
  BC-2   :107   1st Qu.:1994-09-21   Cl  :148   1st Qu.:  14.03
  BC-1   : 62   Median :1996-05-21   Cond: 94   Median :  64.40
  BC-4   : 38   Mean   :1998-11-19   Mg  : 65   Mean   : 189.47
  BC-1.5 : 28   3rd Qu.:2002-10-31   Na  : 34   3rd Qu.: 285.75
  BC-0.5 : 12   Max.   :2011-05-18   SO4 :155   Max.   :2058.00
  (Other): 11                        TDS :157   NA's   :   8.00

   Bottom row of the 'param' column.

Rich