[R] datetime data and plotting

[Gabor Grothendieck]

The problem is related to time zones.  The easiest way to
handle this is to avoid using POSIXt and use chron instead
so you don't have to worry about them.

require(chron)
day <- 6:16
dts <- dates(paste("10", day, "03", sep="/"))
plot(dts,day)
abline(v=dts)

 
---
From: Jacob Etches <jetches at iwh.on.ca>
 
If I take the following simple data:

YEAR MONTH DAY WEIGHT.KG
2003 10 6 1.2
2003 10 12 1.2
2003 10 16 1.3

and format the date data and plot it:

dates <- strptime(paste(DAY,MONTH,YEAR),"%d%m%Y")
plot(c(min(dates),max(dates)),c(0,max(WEIGHT.KG)),
xlab="Date",ylab="Weight (kg)",type="n")
lines(dates,WEIGHT.KG)
points(dates,WEIGHT.KG)

I find that the data points are all plotted at (x-1,y),
where x is in days. Have I requested this behaviour 
accidentally? I'm using R-1.8 on OS X.

Printing the dates object looks correct, and simple 
manipulations such as max(dates)-min(dates) behave 
normally.

Jacob Etches

Doctoral candidate
Dept of Public Health Sciences
University of Toronto



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