[R] plot time series / dates (basic)

[bogdan romocea]

Dear R users,

I'm having a hard time with some very simple things. I have a time
series where the dates are in the format 7-Oct-04. I imported the
file with read.csv so the date column is a factor. The series is
rather long and I want to plot it piece by piece. The function below
works fine, except that the labels for date are meaningless (ie
9.47e+08 or 1098000000 - apparently the number of seconds since
whatever). I don't want to convert the data frame to a ts object
because there are missing days and I don't want any interpolation.

1. How do I replace the date labels with something like 'Mar04',
instead of 9.47e+08 / 1098000000?

2. In the PDF file, the space between the two graphs printed pair by
pair is fairly large. Can I remove/reduce the area that seems
reserved for Title and X label so that, on a page, the space between
the graph at the top and the one at the bottom is minimized?

3. Given the function below, I haven't discovered a way to have
"vara" appear as the Title or Y label in graphs.
main=as.character(vara) lists all the values of vara (which is a
column from the data frame d). So, how can I use the name of a vector
as title or label in a plot?

Thank you,
b.


d <- ('data.csv', header = T, sep = ",", quote="", dec=".", 
	fill = T, skip=0)
attach(d)
#function to plot a long time series piece by piece
pl <- function(vara, varb, points)
	{
	date <- as.POSIXct(strptime(as.character(Date), "%d-%b-%y"), tz =
"GMT")
	pr1 <- vector(mode="numeric")
	pr2 <- vector(mode="numeric")
	dat <- vector()
	for (j in 1:(round(length(Vol)/points)+1)) #number of plots
		{
		for (i in ((j-1)*points+1):(j*points)) 
			{
			pr1[i-points*(j-1)] <- vara[i]
			pr2[i-points*(j-1)] <- varb[i]
			dat[i-points*(j-1)] <- date[i]
			}
		par(mfrow=c(2,1)) 
		plot(dat, pr1, type="b")
		plot(dat, pr2, type="b")
		}
	}

pdf("Rplots.pdf")
pl(Vol, atr, 50)
dev.off()





		
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