[R] increase number of ticks on x axis of dates

[Graves, Gregory]

My x axis is a series of daily dates (e.g., 01/01/2000, 01/02/2000,
etc.) from 2000 to end of 2008.  The default only gives me 4 ticks.  I
want more.  Why doesn't this work?

sdate<-as.POSIXct(strptime(date,format="%m/%d/%Y")) 
       
plot(ppt~sdate,type="l",ylim=c(0,47),col=1,lwd=1,pch=16,ylab="Salinity,
psu",xlab="Year",las=1,main="Duck Key Salinity",xaxt="n")

year.text=c("2001","2002","2003","2004", "2005", "2006", "2007","2008",
"2009")

axis(1, at=c(1:9),labels=year.text)



Gregory A. Graves
Lead Scientist
REstoration COoordination and VERification (RECOVER) 
Watershed Division
South Florida Water Management District
Phones:  DESK: 561 / 682 - 2429 
             CELL:  561 / 719 - 8157