R help - Dec 2004 - Drawing a rectangle around a barplot()

Hi

I want to draw a rectangle behind a barplot such that it highlights
those particular bars from the rest of the plot.  I have figured out how
to draw a barplot(), and then how to draw a rectangle of the correct
shape and size (using rect()), but when I use rect() it draws over the
top of the bars, and then when I re-draw the bars, it draws with a white
background, thus eliminating my rectangle!  I can't use box() as I don't
want to draw a box round my entire plot, I just want to draw a box as
the background to certain subsets of the bars.

Can anyone help?  (those of you familiar with microsoft word/excel
drawing tools, I want something similar to the command "send to back"
such that one drawing object is placed behind the others)

Thanks in advance

Mick

michael watson (IAH-C) wrote:
> Hi
> 
>  I can't use box() as I don't
> want to draw a box round my entire plot, I just want to draw a box as
> the background to certain subsets of the bars.
   One idea. Edit the barplot.default function so it doesnt call plot.new.

  do:

  myBarplot = barplot.default

  then edit the myBarplot function. Add an extra parameter to the 
argument list 'add', and make it False by default:

             cex.names = par("cex.axis"), inside = TRUE, plot = TRUE,
             axis.lty = 0, add=F, ...)

  then find plot.new and wrap it in a condition:

     if(!add)plot.new()

  Now try:

  tN <- table(Ni <- rpois(100, lambda=5))
  myBarplot(tN)
  rect(2,1,6.5,8.5)

  - this puts the rectangle on top of the bars, which you dont want, so 
you call myBarplot with add=T so that plot.new isnt called and the 
barplot appears over the rectangle:

  myBarplot(tN,add=T)

works for me, if I understand your problem correctly!

Baz

Thanks!

Barry's suggestion did the trick.  

Mick
-----Original Message-----
From: Marc Schwartz [mailto:MSchwartz at MedAnalytics.com] 
Sent: 02 December 2004 13:10
To: Barry Rowlingson
Cc: michael watson (IAH-C); R-Help
Subject: Re: [R] Drawing a rectangle around a barplot()


On Thu, 2004-12-02 at 11:07 +0000, Barry Rowlingson
wrote:
> michael watson (IAH-C) wrote:
> > Hi
> > 
> >  I can't use box() as I don't
> > want to draw a box round my entire plot, I just want to draw a box 
> > as the background to certain subsets of the bars.
> 
>    One idea. Edit the barplot.default function so it doesnt call 
> plot.new.
> 
>   do:
> 
>   myBarplot = barplot.default
> 
>   then edit the myBarplot function. Add an extra parameter to the
> argument list 'add', and make it False by default:
> 
>              cex.names = par("cex.axis"), inside = TRUE, plot =
TRUE,
>              axis.lty = 0, add=F, ...)
> 
>   then find plot.new and wrap it in a condition:
> 
>      if(!add)plot.new()
> 
>   Now try:
> 
>   tN <- table(Ni <- rpois(100, lambda=5))
>   myBarplot(tN)
>   rect(2,1,6.5,8.5)
> 
>   - this puts the rectangle on top of the bars, which you dont want, 
> so
> you call myBarplot with add=T so that plot.new isnt called and the 
> barplot appears over the rectangle:
> 
>   myBarplot(tN,add=T)
> 
> works for me, if I understand your problem correctly!
> 
> Baz

In follow up to Baz' post, the 'add' argument is already in the 
barplot2() function, which is in the gregmisc bundle (gplots package) on
CRAN.

I have also been looking at adding a 'panel.first' and
'panel.last'
argument to barplot2, to enable functionality similar to that of
plot.default(). This would provide the ability to add additional plot
components before and/or after the bars are drawn. I'll get to that as
soon as time permits.

HTH,

Marc Schwartz