R help - Jan 2005 - forcing all tick labels to plot

I'm trying to find a way to force all the x-axis tick labels to plot, 
regardless whether or not they overlap or look pretty.

V is a factor with, say, 4 levels.  A call to plot(V) gives a 
histogram-like plot, one bar for each level in V.  The problem is that 
all the label names may not be plotted because some of the names are 
lengthy and would tend to overlap if plotted.

I don't care if they do, I want to see all the labels, overplotted or not.

I tried:

     plot(V,axes=F)
     d<-levels(V)
     axis(1,at=1:4,label=d)
     axis(2)

But this does nothing more than the default, that is, only some of the 
labels print.  The other problem is the "at=1:4", which is my guessing
where the tickmarks go.  The function "axTicks(1)" may help, but it 
frequently has more tick marks then levels in "V", so again I have to 
guess which goes where.

I see this:

     c<-par()
     c$xaxp = 0.5 3.5 4

or something similar.  Is there another par() in which the tick marks 
that are calculated are given explicitly?

I have tried:

     par(cex=.7)

and that works for some V, but not for all, and it isn't a very general 
solution.

Is there some flag that I can set to force all the tick labels to plot?

Matt Briggs

On Wed, 2005-01-19 at 15:43 -0500, William Briggs wrote:
> I'm trying to find a way to force all the x-axis tick labels to plot, 
> regardless whether or not they overlap or look pretty.
> 
> V is a factor with, say, 4 levels.  A call to plot(V) gives a 
> histogram-like plot, one bar for each level in V.  The problem is that 
> all the label names may not be plotted because some of the names are 
> lengthy and would tend to overlap if plotted.
> 
> I don't care if they do, I want to see all the labels, overplotted or
not.
> 
> I tried:
> 
>      plot(V,axes=F)
>      d<-levels(V)
>      axis(1,at=1:4,label=d)
>      axis(2)
> 
> But this does nothing more than the default, that is, only some of the 
> labels print.  The other problem is the "at=1:4", which is my
guessing
> where the tickmarks go.  The function "axTicks(1)" may help, but
it
> frequently has more tick marks then levels in "V", so again I
have to
> guess which goes where.
> 
> I see this:
> 
>      c<-par()
>      c$xaxp = 0.5 3.5 4
> 
> or something similar.  Is there another par() in which the tick marks 
> that are calculated are given explicitly?
> 
> I have tried:
> 
>      par(cex=.7)
> 
> and that works for some V, but not for all, and it isn't a very general
> solution.
> 
> Is there some flag that I can set to force all the tick labels to plot?
> 
> Matt Briggs
plot.factor() is the plot method used in this case. Since it uses
barplot() internally, it will return the bar midpoints invisibly (which
I noted is not defined as a return value in the help for plot.factor)

You can then use mtext() to force the drawing of the labels:

# Draw the plot, but not the x axis
# This example presumes V is a four level factor
mp <- plot(V, xaxt = "n")

# Create some long labels
labels <- c(paste("Very Very Very Long Label Here", 1:4, sep =
""))

# Now plot the labels below the bar midpoint
mtext(side = 1, labels, at= mp, line = 1)

That should do it.

See ?mtext and ?barplot for more information.

HTH,

Marc Schwartz