On Mon, 1 Nov 2004, bogdan romocea wrote:
> 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.
So why use as.POSIXct for a date, rather than as.Date?
> 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?
Just don't convert them to that format. You set up
> dat <- vector()
which is not a dates object. If you use standard R indexing, it will
work. If you throw the class away, it will not. Try
dat <- date[(j-1)*points+1):(j*points)]
etc (no for loop required).
If you want a different format, see ?axis.Date
> 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?
There's a whole chapter on this in `An Introduction to R': have you read
it?
> 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?
That's almost an FAQ. Use deparse(substitute(vara))
> 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()
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595