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.

The original `README’ is appended below.

*** 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.