[R] problems with lattice barchart

[Juan Santos]

   Hello everybody!
    I´m trying to create figures summarizing the abundance of a given species
   (y), by its length classes (x), year (conditional factor) and a grouping
   named as "fraction". I am using the lattice´s barchart but some problems
   arises:
   When  I run the function, the sizes become characters, and this is the
   starting problem for me when trying to adjust the x-axis in order to achieve
   a  good-looking. In  particular,  I  have  found  that  when  range of
   length-classes is high, the output  yield a matted looking in the x-axis,
   which in some cases is unreadable. In order to achieve a wider space between
   x-axis annotations, I was trying to reduce the number of sizes shown in the
   figure,  but so far I got a few improvements in the final results. Here you
   will find a piece of the data frame,
   > x[1:25,]
      Length.class year   fraction     y
   1             6 2006 Fraction.a     0
   2             7 2006 Fraction.a     0
   3             8 2006 Fraction.a   191
   4             9 2006 Fraction.a   784
   5            10 2006 Fraction.a    38
   6            11 2006 Fraction.a  1135
   7            12 2006 Fraction.a  1810
   8            13 2006 Fraction.a  2836
   9            14 2006 Fraction.a  6625
   10           15 2006 Fraction.a  6414
   11           16 2006 Fraction.a 10554
   12           17 2006 Fraction.a 12423
   13           18 2006 Fraction.a 15260
   14           19 2006 Fraction.a 11126
   15           20 2006 Fraction.a  9830
   16           21 2006 Fraction.a  8460
   17           22 2006 Fraction.a  6062
   18           23 2006 Fraction.a  4382
   19           24 2006 Fraction.a  3555
   20           25 2006 Fraction.a  1792
   21           26 2006 Fraction.a  2220
   22           27 2006 Fraction.a  1235
   23           28 2006 Fraction.a   465
   24           29 2006 Fraction.a     0
   25           30 2006 Fraction.a    59
   and this is the  barchart specifications,
   plot.i<-barchart(x[,4]~x[,1]|x[,2],horizontal=F,stack=TRUE,layout=paneis,
   par.settings = simpleTheme(col = c("red3","olivedrab")),groups=x[,3],
   strip = strip.custom (bg = c('transparent'),par.strip.text = list(cex =
   0.8)),auto.key=list(columns=2),
   panel=function(...,box.width,border){
   panel.grid(h=-1,v=0)
   panel.abline(v=TML,col="red",lty=2)
   panel.barchart(...,box.width = .99,border="black")},
   ,xlab="Length Size",ylab="Y")
   Can someone guide me to solve the problem?

   --