[R] Date problem

[Moshe Olshansky]

Try the xlsReadWrite package from CRAN.

--- Mr Natural <drstrong at ucdavis.edu> wrote:

> 
> Dear Natalia:
> I have had the same problem. Solved it by keeping my
> dates in Excel files
> with the rest of my data. When I want to do
> something in R, highlight the
> date column and format it as "general" You will get
> a 5 digit number that
> represents the Julian date (more digits if you have
> minutes and seconds).
> Save the Excel file as a csv file.
> Then read it into R making the variables all
> numeric, with use of
> columnClasses,
> eg. from a big file  that Im working on now,
> 
>
ss<-read.csv("six.sites.epn.hist.csv",strip.white=T,na.strings=".",
> colClasses=c("numeric","numeric","numeric",
> "numeric","numeric","numeric",
> "numeric","numeric","numeric",
> "numeric","numeric","numeric",
> "numeric","numeric","numeric",
> "numeric","numeric","numeric",na.rm=T ))
> 
> Then you make the Julian dates back into calendar
> dates that plot so nicely
> in R.
> In my file, I have one date column for every y
> variable because each has a
> different sequence of dates.
> Note that Excel and R have a different Julian "day
> 1." Excel is Jan 1 1900,
> and R is Jan 1 1970.
> You set the day one Julian date in R with the origin
> feature in the dates().
> 
> The six interesting "y" variables (MP,C,D,UD,LD,and
> BS) each have two date
> columns, the most interesting of which is the
> calendar date, which are made
> from the Julian dates that I read in.
> 
> dmp<-dates(ss$MPdate,origin=c(month = 1, day = 1,
> year = 1900))
> dc<-dates(ss$Cdate,origin=c(month = 1, day = 1, year
> = 1900))
> dd<-dates(ss$Ddate,origin=c(month = 1, day = 1, year
> = 1900))
> dld<-dates(ss$LDdate,origin=c(month = 1, day = 1,
> year = 1900))
> dud<-dates(ss$UDdate,origin=c(month = 1, day = 1,
> year = 1900))
> dbs<-dates(ss$BSdate,origin=c(month = 1, day = 1,
> year = 1900))
> 
> Then, I plot a stack of 6 time series, one on top of
> each other.
> Note that I used "arrow" for error bars.
> #stack of plots, one for each site.
> attach(ss)
> 
> par(mar=c(2,2,1,1), mfrow = c(6,1))
> plot(MP~dmp, type="b",xlab="",ylim=c(0,1),xaxt =
> "n")
>
arrows(dmp,MP+semp,dmp,MP-semp,length=.02,angle=90,code=3)
> plot(C~dc, type="b",xlab="",ylim=c(0,1),xaxt = "n")
> arrows(dc,C+sec,dc,C-sec,length=.02,angle=90,code=3)
> plot(D~dd, type="b",xlab="",ylim=c(0,1),xaxt = "n")
> arrows(dd,D+sed,dd,D-sed,length=.02,angle=90,code=3)
> plot(LD~dld, type="b",xlab="",ylim=c(0,1),xaxt =
> "n")
>
arrows(dld,LD+seld,dld,LD-seld,length=.02,angle=90,code=3)
> plot(UD~dud, type="b",xlab="",ylim=c(0,1),xaxt =
> "n")
>
arrows(dud,UD+seud,dud,UD-seud,length=.02,angle=90,code=3)
> plot(BS~dbs, type="b",xlab="",ylim=c(0,1))
>
arrows(dbs,BS+sebs,dbs,BS-sebs,length=.02,angle=90,code=3)
> 
> 
> 
> I hope this helps, 
> Don
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> natalia norden wrote:
> > 
> > Hello,
> > I have some "stupid" problems managing "date"
> data.
> > I have a colomn "date", which I converted from a
> character representation:
> > 
> > for example:
> > a="26/02/06"
> > date=strptime(a,format="%d/%m/%y")
> > 
> > For one part of the analysis, I'm interested only
> in the month and the 
> > year, so I did:
> > 
> > m.y=strftime(date,format="%m/%y")
> > 
> > This returns me "02/06", but this is an object of
> class "character" and 
> > I can't convert it into an object of class "Date".
> Doing 
> > strptime(m.y,format="%m/%y") or
> as.Date(m.y,format="%m/%y") returns me NA
> > 
> > How can a convert this colomn "m.y" in a Date
> class?
> > 
> > Actually, I need it to plot fruiting data against
> time (month and year).
> > Because I have many values of seeds in a month, I
> used the function
> > tapply:
> > seeds=tapply(data$seed,data$m.y,sum)
> > But plot(x=names(seeds),y=seeds) doesn't work.
> Does anyone know an 
> > easier way?
> > 
> > Thank you for your time,
> > natalia
> > 
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> > http://www.R-project.org/posting-guide.html
> > 
> > 
> 
> -- 
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>
http://www.nabble.com/Date-problem-tf1280528.html#a11660658
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> 
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