R help - Jun 2005 - How to rotate the axisnames in a BARPLOT

Hi all,

- how can I do a barplot with rotated axis labels? I've seen the example for
just a plot in the FAQ, but I'll missing the coordinates to plot my text at
the right position beneath the bars. 
Is there any (easy?) solution?

- how can I set the y-axis in a barplot to logarithmic scale?

Many thanks in advance!

Best Regards
 Tom

--

On Thu, 2005-06-30 at 23:05 +0200, hulubu at gmx.de
wrote:
> Hi all,
> 
> - how can I do a barplot with rotated axis labels? I've seen the
example for
> just a plot in the FAQ, but I'll missing the coordinates to plot my
text at
> the right position beneath the bars. 
> Is there any (easy?) solution?
> 
> - how can I set the y-axis in a barplot to logarithmic scale?
> 
> Many thanks in advance!
> 
> Best Regards
>  Tom
The same concept for rotating axis labels in a regular plot per the FAQ
can be used in a barplot, as long as you know that barplot() returns the
bar midpoints. So:

     ## Increase bottom margin to make room for rotated labels
     par(mar = c(7, 4, 4, 2) + 0.1)

     ## Create plot and get bar midpoints in 'mp'
     mp <- barplot(1:10)

     ## Set up x axis with tick marks alone
     axis(1, at = mp, labels = FALSE)

     ## Create some text labels
     labels <- paste("Label", 1:10, sep = " ")

     ## Plot x axis labels at mp
     text(mp, par("usr")[3] - 0.5, srt = 45, adj = 1,
          labels = labels, xpd = TRUE)

     ## Plot x axis label at line 4
     mtext(1, text = "X Axis Label", line = 4)

See ?barplot for more information.

With respect to the log scales, you would need to use barplot2(), which
is in the 'gplots' package on CRAN. barplot2() supports log scales using
the same 'log' argument as plot().

HTH,

Marc Schwartz

Try the following.  I made this based on the eaxmple from FAQ 7.27

tab=table(rpois(100, 2))  #Creates table to make a barplot
par(mar = c(6, 4, 4, 2) + 0.1)#Prepares margin to fit x axis labels
pts=barplot(tab, xaxt = "n", xlab = "",
col="yellow2")#Barplot of tab
without x axis or label.
#Also stores the middle points of the bars

axis(side=1,at=pts, labels=F, tick=T)#Creates x axis with tickmarks exactly 
at the middle of the bars
nam=paste("Text",names(tab))#Names of each category. To be used on
labels

text(pts, par("usr")[3] - 1.5, srt = 45, adj = 1, labels = nam, xpd =
TRUE)
#Adds the tickmark labels
# adj = 1 will place the text at the end ot the tick marks
# xpd = TRUE will "clip" text outside the plot region

mtext(1, text = "My Axis Label", line = 4) #Adds x axis label at line
2

Second hit of  RSiteSearch("logarithmic axis barplot") takes you to
barplot2
{gplots}


Cheers

Francisco
>From: hulubu at gmx.de
>To: r-help at stat.math.ethz.ch
>Subject: [R] How to rotate the axisnames in a BARPLOT
>Date: Thu, 30 Jun 2005 23:05:15 +0200 (MEST)
>
>Hi all,
>
>- how can I do a barplot with rotated axis labels? I've seen the example
>for
>just a plot in the FAQ, but I'll missing the coordinates to plot my text
at
>the right position beneath the bars.
>Is there any (easy?) solution?
>
>- how can I set the y-axis in a barplot to logarithmic scale?
>
>Many thanks in advance!
>
>Best Regards
>  Tom
>
>--
>
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