[R] reducing distances between tickmarks

[Dimitri Liakhovitski]

Hello, everybody!
I have a code below that creates a data set and then a stacked bar
chart based on that data set.
No need to look at it - just notice please that my horizontal axis is
a date varible (x=my.data$date).
I have a question about the last 2 lines of this code:
grid(nx=NULL,ny=NULL,col = "lightgray", lty = "dotted",lwd = par("lwd"))
axis(1, las = 2)

Could anyone tell me - what are the tick mark labels on my X axis? Why
are they not dates?
axTicks(side=1)

Is there any way to change them to actual dates as in my.data$date?
And also - is there a way to force the graph to display all tickmarks
on X axis - and not just 4 of them?

Thank you!
Dimitri

my.data<-data.frame(date=c(20080301,20080401,20080501,20080601,20080701,20080801,20080901,20081001,20081101,20081201,20090101,20090201,20090301,20090401,20090501,20090601,20090701,20090801,20090901,20091001,20091101,20091201,20100101,20100201,20100301,20100402,20100503),
x=c(1.1, 1, 1.6, 1, 2, 1.5, 2.1, 1.3, 1.9, 1.1, 1, 1.6, 1, 2, 1.5,
2.1, 1.3, 1.9, 1.1, 1, 1.6, 1, 2, 1.5, 2.1, 1.3, 1.9),
y=c(-4,-3,-6,-5,-7,-5.2,-6,-4,-4.9,-4,-3,-6,-5,-7,-5.2,-6,-4,-4.9,-4,-3,-6,-5,-7,-5.2,-6,-4,-4.9),
z=c(-0.2,-0.3,-0.4,-0.1,-0.2,-0.05,-0.2,-0.15,-0.06,-0.2,-0.3,-0.4,-0.1,-0.2,-0.05,-0.2,-0.15,-0.06,-0.06,-0.2,-0.3,-0.4,-0.1,-0.2,-0.05,-0.2,-0.15),
a=c(10,13,15,15,16,17,15,16,14,10,13,15,15,16,17,15,16,14,10,13,15,15,16,17,15,16,14))
my.data$date<-as.character(my.data$date)
my.data$date<-as.Date(my.data$date,"%Y%m%d")
(my.data)
str(my.data)

positives<-which(colSums(my.data[2:ncol(my.data)])>0) # which vars
have positive column sums?
negatives<-which(colSums(my.data[2:ncol(my.data)])<0) # which vars
have negative column sums?

y.max<-1.1*max(rowSums(my.data[names(positives)])) # the max on the y
axis of the chart
y.min<-1.1*min(rowSums(my.data[names(negatives)])) # the min on the y
axis of the chart
ylim <- c(y.min, y.max)
order.positives<-rev(rank(positives))
order.of.pos.vars<-names(order.positives)
order.negatives<-rev(rank(negatives))
order.of.neg.vars<-names(order.negatives)
order<-c(order.negatives,order.positives)
order.of.vars<-names(order)   # the order of variables on the chart -
from the bottom up
### so, the bottom-most area should be for z, the second from the
bottom area- for y (above z)

all.colors<-c('red','blue','green','orange','yellow','purple')
xx <- c(my.data$date, rev(my.data$date))
bottom.y.coordinates<-rowSums(my.data[names(negatives)])

plot(x=my.data$date, y=bottom.y.coordinates, ylim=ylim, col='white',
type='l', xaxt='n',
	ylab='Title for Y', xlab='Date', main='Chart Title')

for(var in order.of.neg.vars){
	top.line.coords<-bottom.y.coordinates-my.data[[var]]
	bottom.coords<-c(bottom.y.coordinates,rev(top.line.coords))
	polygon(xx,bottom.coords,col=all.colors[which(names(my.data) %in% var)])
	bottom.y.coordinates<-top.line.coords
}

for(var in order.of.pos.vars){
	top.line.coords<-bottom.y.coordinates+my.data[[var]]
	bottom.coords<-c(bottom.y.coordinates,rev(top.line.coords))
	polygon(xx,bottom.coords,col=all.colors[which(names(my.data) %in% var)])
	bottom.y.coordinates<-top.line.coords
}

grid(nx=NULL,ny=NULL,col = "lightgray", lty = "dotted",lwd = par("lwd"))
axis(1, las = 2)


-- 
Dimitri Liakhovitski
Ninah Consulting
www.ninah.com