trouble positioning legends on barplot written to a file - R-help

Tue, Nov 12, 2002 3:19 PM #

You might consider putting the legend in a separate plot area.  For
instance, using the layout function:

library(grid)
data(VADeaths, package = "base")
layout( cbind(1,2), widths=c(8,3) )  # make two plotting areas, 
                                     #   8 and 3 units wide
barplot(VADeaths, plot = TRUE)       # generate the barplot
plot.new()                           # move to the new region
legend(x=0.5,y=0.5,letters[1:5],     # center a legend in the new
       fill=heat.colors(5)[1:5],     #   plot region
       xjust=0.5,yjust=0.5)

-Greg

-----Original Message-----
From: Tom Arnold [mailto:tarnold at smpllc.com]
Sent: Tuesday, November 12, 2002 12:40 PM
To: r-help at stat.math.ethz.ch
Subject: [R] trouble positioning legends on barplot written to a file

I'm trying to generate some plots for print publication and 
I'm having trouble
getting them the way I want. I get a plot with a legend that 
overlaps the bars
and looks bad. Also, I'm saving this as PDF file (whatever 
happened to the
"png" function to save as PNG format, in r 1.4.1?)

I've tried a number of things, which produce a number of questions.

1) it seems that the "legend" for a plot must be within the 
plot area. Is
there a way to put the legend above, below, or to the side of 
the plot? The
particular data I have fill up the plotting area (stacked bar 
charts, going to
100% in each bar)

2) I've tried using "locator()" to position the legend. This 
only works, so
far, if I am not using trying to divert output to another 
device -- like
creating a PDF via
pdf();
barplot(resultmat);
dev.off();

so if I take out the pdf() and the dev.off() and just do this:
barplot(resultmat);
legend(locator(1),legend=l,fill=colors);

it works, on the graphics display device window on screen.

However, if I do this:
pdf(onefile=FALSE);
barplot(resultmat);
legend(locator(1),legend=l,fill=colors);
dev.off();

I get:

Error in legend(locator(1),legend = l : missing y

Also it doesn't let me specify a point. I suppose that's not 
so surprising,
because it is drawing to a non-interactive graphics device 
(the PDF "device"
is non-interactive, right?), but the error message is confusing.

So, is there any way to specify the location with locator() 
AND to save that
plot to a file?

And if I don't use "locator' then I have to specify the 
legend location to
"legend(x,y, legend) but the documentation doesn't say what 
coordinate system
that's supposed to be in.

TIA.

Tom Arnold

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