The R Project SVN R-packages

This directory contains code and help for an R port of CHRON, an S-PLUS
package for working with chronological objects (times and dates).

The original was downloaded from
  http://netlib.bell-labs.com/cm/ms/departments/sia/project/misc/chron.html
See the file `PORTING' for the changes made for the R version.

See `Y2K' for information on a recent year 2000 update.

The original `README' is appended below.  See `COPYING' for copyright
information.

KH <Kurt.Hornik@ci.tuwien.ac.at> 1998/02/13

*** Original README **************************************************

This directory contains S functions to work with chron objects. These
objects handle dates and times. For the time being issues relating to 
time-zones, daylight savings time, etc. are being put aside.

NOTE: To use chron objects you need library(statistics) in S.
      In S-PLUS you need library(chron, first = T)

For source and details, see

    http://cm.bell-labs.com/ms/departments/sia/dj/chron.html

The following methods and functions are available for chron objects:

function    description
----------  -----------------------------------------------------
chron       createas a chron object; it takes either julian dates
        or character dates. See help(chron).
dates       creates a dates object (simply invokes chron)
times       creates a times object (simply inoveks chron)

as.numeric  returns a vector of julian dates + fraction of day (times)
as.character    returns a character representation of dates/times
is.na

print       print dates and times nicely 
plot        plot with time axis
hist        histogram with time axis
identify    identify points in scatterplot
lines, points   add lines/points
axis.times  add time axis to plot
cut     make ordered factors from dates (e.g., by month, week)
seq     generate a sequence of dates

min, max,   numeric summaries
range, summary      
sort, order
trunc, ceiling,
round, signif,
diff

[.times     selects, e.g., dates[ dates > "02/20/92" ], or
        lathe.date[ start.date > min(scan.date) ]

[<-.times   replacement
c       combines chrons

days, months,   extact day, month, year, quarter number, etc.
years, quarters     
weekdays,
hours, minutes, 
seconds
is.holiday
is.weekend

month.day.year  date conversion (modified from the S "blue" book) 
julian,
day.of.week

UNDOCUMENTED FEATURES:
----------------------
    1. Chron matrices can be created from chron objects by using dim() 
       (can't use matrix() nor array())
       > dim(x) <- c(20,3)
       > x[2,3] <- "03/28/90"    # replaces a cell

    2. The c() method takes anything that can be coerced to chrons:
       y <- c(x, "03/21/92", 8123)
       but a bug(?) in the S evaluator makes it necessary to 
       specify the chron object first, i.e., c("03/28/90", x) does not
       dispath the c.dates() method.