R help - Feb 2010 - lattice barchart using a time scale in x axis

I'm trying to produce a barchart plot with groups, in which each group is
placed in a particular
time scale in x-axis. If I use barchart directly it does not take the time
scale. I've tried with
xyplot and adding a panel.barchart, I have the bars in the right place, but not
the three groups I'm
trying to produce. I've tried defining panel and panel.group, but can't
get it to work
Drate is a numeric variable with three categories, perc a percentage of preys
digested.

Script with barchart:
barchart(Perc~as.POSIXct(hora,format="%d-%m-%Y
%H:%M"),digrate,groups=Drate,horizontal=F, key = leg,
  
scales=list(alternating=F,tck=c(1,0),x=list(at=1:10,labels=format(seq(r[1],r[2],"hours"),
     format="%H:%M"))),
             panel=function(x,y,...) {panel.fill(col="white")
            
panel.barchart(x,y,col=c("white","grey","black"),...)}
             )

SCript with xyplot:
xyplot(Perc~as.POSIXct(hora,format="%d-%m-%Y
%H:%M"),digrate,groups=digrate$Drate,key=leg,xlab="time
of the day",
 
scales=list(alternating=F,tck=c(1,0),x=list(at=seq(r[1],r[2],by="hour"),labels=format(seq(r[1],r[2],"hours"),format="%H:%M"))),
             panel=function(x,y,groups,...) {
         panel.fill(col="white")
         panel.barchart(x,y,groups,horizontal=F,box.ratio=1000,stack=F,...)}
       )

Fran

> SCript with xyplot:
> xyplot(Perc~as.POSIXct(hora,format="%d-%m-%Y
> %H:%M"),digrate,groups=digrate$Drate,key=leg,xlab="time of the
day",
>
>
scales=list(alternating=F,tck=c(1,0),x=list(at=seq(r[1],r[2],by="hour"),labels=format(seq(r[1],r[2],"hours"),format="%H:%M"))),
> ? ? ? ? ? ?panel=function(x,y,groups,...) {
> ? ? ? ?panel.fill(col="white")
> ? ? ? ?panel.barchart(x,y,groups,horizontal=F,box.ratio=1000,stack=F,...)}
> ? ? ?)
>
> Fran
You do need to use xyplot() to get control of the x axis.  In this
example, the problem
comes from not specifying the arguments names to panel.barchart.  In
?panel.barchart,
the third argument is box.ratio.  The value of your groups was
therefore used as the box.ratio
and the widths of the boxes differed by group.  Here is a complete
working example, with fake
data and without r and leg.

digrate <- data.frame(Perc=runif(30), Drate=rep(letters[1:3], 10),
                  hora=rep(c(1,2,3,6,8,10,15,20,24,30),each=3))
digrate

xyplot(Perc~hora, ## as.POSIXct(hora,format="%d-%m-%Y %H:%M"),
       data=digrate, groups=digrate$Drate, ## key=leg,
       xlab="time of the day",
       scales=list(alternating=FALSE,tck=c(1,0) ##,
         ## x=list(
         ##   at=seq(r[1],r[2],by="hour"),
         ##   labels=format(seq(r[1],r[2],"hours"),
format="%H:%M"))
         ),
       panel=function(x,y,groups,...) {
         panel.fill(col="white")
         panel.barchart(x, y, groups=groups, horizontal=FALSE,
                        box.ratio=5, stack=FALSE, ...)
       },
       main="xyplot"
       )

Hi all,
Thanks for your answers, it worked, but still can't get the time scale on
the x-axis, probably has
to do with the unit in the viewport or something like that. But following your
recommendation I've
prepared some dummy data to go with the scripts. As before we have two graphs,
one that has the
error I got, and another that has the graph I want to get, but without the time
scale as needed.
Cheers,
Fran
Example:

#create the dummy data
digrate <- data.frame(Perc=runif(30), Drate=rep(letters[1:3], 10),
                  
date=c(rep("26-06-2010",9),rep("27-06-2010",21)),
 
hour=rep(c("18:00","20:00","23:00","03:00","05:30","08:00","10:00","14:40","17:30","19:30"),each=3))
digrate$hora<-paste(digrate$date,digrate$hour)
digrate
library(lattice)
# xyplot with panel.barchart, but does not take the groups as in example 2
xyplot(Perc~as.POSIXct(hora,format="%d-%m-%Y
%H:%M",origin=strptime(digrate$hora,"%d-%m-%Y %H:%M")),
        data=digrate, groups=digrate$Drate, ## key=leg,
        xlab="time of the day",
       
scales=list(alternating=FALSE,tck=c(1,0),x=list(at=seq(r[1],r[2],by="hour"),
          labels=format(seq(r[1],r[2],"hours"),
format="%H:%M"))),
        panel=function(x,y,groups,...) {
          panel.fill(col="white")
          panel.barchart(x, y, groups=groups, horizontal=FALSE,
                         box.ratio=5000, stack=FALSE, ...)
        },
        main="xyplot"
        )

# barchart example does not get the time scale
# get the time range for the x-axes in graph 2
r<-range(strptime(digrate$hora,"%d-%m-%Y %H:%M"))
barchart(Perc~as.POSIXct(hora,format="%d-%m-%Y
%H:%M"),digrate,groups=Drate,horizontal=F,
  
scales=list(alternating=F,tck=c(1,0),x=list(at=1:10,labels=format(seq(r[1],r[2],"hours"),
     format="%H:%M"))),
             panel=function(x,y,...) {panel.fill(col="white")
                 panel.grid(-1,0,lty=3,col="black")
                
panel.barchart(x,y,col=c("white","grey","black"),...)}
             )


On 05/02/2010 1:56, RICHARD M. HEIBERGER wrote:
> Fran,
>
> Please send to the list some properly structured dummy data.
> dput(digrate.dummy) would be easiest for me.
>
> Rich
>
>