Greetings I am attempting to plot observations of a cave aquatic invertebrate dating from 1901-2004. I can come up with a nice lattice plot of the eight sites from which I have data easily enough. However, I'd like to be able to highlight the 0 observations on the plots, i.e., attempts to find it at the site were unsuccessful. I'd like to be able to highlight these observations with either a symbol or a color. Here's a sample of the data (Reach=site): (Embedded image moved to file: pic17437.jpg) Here's my code for the plot: xyplot(No.Invert~Year|Reach, data=Invert.Coll.1901.2004, layout=c(4,2), ylab="No. Invert 'collected'", scales=list(x=list(rot=45))) *************************************************************** Kurt Lewis Helf, Ph.D. Ecologist EEO Counselor National Park Service Cumberland Piedmont Network P.O. Box 8 OR NPS Warehouse 61 Maintenance Rd. Mammoth Cave, KY 42259 Ph: 270-758-2163 Lab: 270-758-2151 Fax: 270-758-2609 Cumberland Piedmont Network (CUPN) Homepage: http://tiny.cc/e7cdx *************************************************************** Science, in constantly seeking real explanations, reveals the true majesty of our world in all its complexity. -Richard Dawkins [Scientific] theories are passed on not as dogmas but rather with the challenge to discuss them and improve upon them. -Karl Popper ...consider yourself a guest in the home of other creatures as significant as yourself. -Wayside at Wilderness Threshold in McKittrick Canyon, Guadalupe Mountains National Park, TX CUPN Forest Pest Monitoring Website: http://bit.ly/9rhUZQ CUPN Cave Cricket Monitoring Website: http://tiny.cc/ntcql CUPN Cave Aquatic Biota Monitoring Website: http://tiny.cc/n2z1o