R help - Feb 2008 - Avoiding overplotting of text.

Hi all,

I am plotting some data, and use text() to get variable names next to
points on the graph. What is the best way to make sure that these text
labels are readable and not overlapping when two datapoints are close?
I've tried using jitter(), but the effect is random and doesn't always
give a good result.
Any suggestions would be most appreciated.

Best regards,

Gustaf

Example:
--------------
 x<-rnorm(20)
 x.labels<-vector(length=length(x))
 for(i in
1:length(x))x.labels[i]<-paste(sample(LETTERS,5,replace=T),collapse="")
 y<-rnorm(length(x))
 plot(x,y)
 text(x,y,x.labels)
###Most of the time some of the labels end up unreadable. ####
-------------------

-- 
Gustaf Rydevik, M.Sci.
tel: +46(0)703 051 451
address:Essingetorget 40,112 66 Stockholm, SE
skype:gustaf_rydevik

> I am plotting some data, and use text() to get variable names next to
> points on the graph. What is the best way to make sure that these text
> labels are readable and not overlapping when two datapoints are close?
> I've tried using jitter(), but the effect is random and doesn't
always
> give a good result.
It is probably possible to calculate the space that each label takes up on 
the page, and write some logic to automatically reposition the labels. 
This however is almost certainly very tricky to do properly.  The easier 
options are:

1. If you only have a few labels, and it's just one or two graphs, 
manually reposition them.
2. Make the text smaller and/or make the device size larger.
3. Draw the labels in different colours so that they can be distinguished 
even when they overlap.
4. Don't draw the labels on the plotting region; use a key instead.

Regards,
Richie.

Mathematical Sciences Unit
HSL


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Gustaf Rydevik wrote:
> Hi all,
> 
> I am plotting some data, and use text() to get variable names next to
> points on the graph. What is the best way to make sure that these text
> labels are readable and not overlapping when two datapoints are close?
> I've tried using jitter(), but the effect is random and doesn't
always
> give a good result.
> Any suggestions would be most appreciated.
> 
Hi Gustaf,
Have a look at thigmophobe.labels in the plotrix package.

Jim

>  I am plotting some data, and use text() to get variable names next to
>  points on the graph. What is the best way to make sure that these text
>  labels are readable and not overlapping when two datapoints are close?
>  I've tried using jitter(), but the effect is random and doesn't
always
>  give a good result.
>  Any suggestions would be most appreciated.
Have a look at pointLabel in maptools -
http://finzi.psych.upenn.edu/R/library/maptools/html/pointLabel.html


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