[R] overlapping labels

[Gavin Simpson]

Duncan Murdoch wrote:
> On 12/3/2007 12:21 PM, Biscarini, Filippo wrote:
>> Good evening,
>>  
>> I am trying to add labels to the point of a simple plot, using the
>> text() function; the problem is that sometimes, if two points are too
>> close to each other, labels overlap and are no longer readable.
>> I was wondering whether there are options that I can use to prevent this
>> overlapping (by, for example, placing labels alternatively above and
>> below the plotted curve), or whether I should use another set of
>> graphical functions (grid or lattice packages).
>> Does anybody have suggestions?
> 
> I don't think there are any functions to automatically avoid overlaps, 
> but it is not hard to manually move some of the labels.  

The OP might like to take a look at the orditorp function in package 
vegan, which is designed to add information from complex ecological 
data sets with many species to ordinations. It works out if a label 
can be placed and if not draws a point. The OP would have to modify it 
to try another place to plot, but that might be a basis from which to 
work.

Of course, if this is a one-off project Duncan's solution is more than 
adequate.

G

For example,
> you could alternate labels above and below with code like this:
> 
>  > x <- 1:10
>  > y <- rep(0, 10)
>  > plot(x,y)
>  > text(x, y, rep("label", 10), pos=rep(c(1,3), 5))
> 
> because the pos parameter can be specified separately for each observation.
> 
> Duncan Murdoch
> 
>>  
>> Thank you,
>>  
>> Filippo Biscarini
>>  
>> PS: These are the lines of codes that I have been using to generate the
>> plot.
>>
>> plot(
>>  prova$x,
>>  prova$y,
>>  type="b",
>>  mar=c(0.5,0.5,0.5,0.5),
>>  xlab="basepairs",
>>  ylab=""
>> );
>>  
>> text(
>>  prova$x,
>>  prova$y,
>>  prova$lab,
>>  pos=3,
>>  offset=2,
>>  cex=0.5
>> );
> 
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