[R] Lattice - parallel: xlim and adding lines

[Sundar Dorai-Raj]

T.A.Wassenaar wrote on 3/29/2005 4:17 PM:
> 
> Hi Sundar,
> 
> Thanks for the reply. And, oops, the panel.parallel.new shouldn't be in 
> there. That is a revised panel function to color according to a group. 
> As with strange, that would generally be 'not-expected', i.e., in the 
> present case, not having an x-axis running from -1 to 1 for all ranges. 
> I would at least expect to have zero in the middle, but that is not so. 
> Excuse me for not expanding 'strange' previously. I have read the 
> guide.., some while ago.
> 
> Thanks again,
> 
> Tsjerk
> 

Tsjerk,

 From panel.parallel, the x values are being scaled to c(0, 1)

x <- (as.numeric(z[subscripts[i], , ]) - llim)/dif

This puts the "Min" at x == 0 and the "Max" at x == 1 on the x-axis. If 
you want to leave it in the raw scale of the x, you will have to write 
your own panel and prepanel function, or simply determine what xlim = 
c(-1, 1) is in the scaled coordinates.

E.g.

lin.scale <- function(x, a = 0, b = 1, new.x = NULL) {
   slope <- (b - a)/diff(range(x))
   inter <- a - slope * min(x)
   if(is.null(new.x)) {
     inter + slope * x
   } else {
     inter + slope * new.x
   }
}
xlim <- lin.scale(range(iris[1:4]), new.x = c(-2, 10))
parallel(~ iris[1:4] | Species, iris, xlim = xlim)

The next question would be how to set the x labels to something other 
than "Min" and "Max" because (to me) they appear to be hard-coded in 
parallel. I will leave that question to Deepayan.

As for adding lines, you will also have to scale your reference line to 
the panel units. For my example, each panel has a x range of c(0, 1) and 
a y range of c(1, 4). E.g.

my.panel.parallel <- function(z, subscripts, col = superpose.line$col,
                               lwd = superpose.line$lwd,
                               lty = superpose.line$lty, ...) {
   superpose.line <- trellis.par.get("superpose.line")
   panel.abline(v = 0.5, lwd = 3)
   panel.parallel(z, subscripts, col, lwd, lty, ...)
}

HTH,

--sundar



> On Tue, 29 Mar 2005 14:42:05 -0600
>  Sundar Dorai-Raj <sundar.dorai-raj at pdf.com> wrote:
> 
>>
>>
>> T.A.Wassenaar wrote on 3/29/2005 2:17 PM:
>>
>>>
>>> Hi,
>>>
>>> I'm trying to set the minimum and maximum in a parallel plot, but 
>>> trying xlim=c(-1,1) gives strange results. Am I missing something? 
>>> The call I give is:
>>>
>>> parallel(~X[,c(6,9,12,15,18)]|X$ff,X,panel=panel.parallel.new,groups=X$protein,layout=c(3,1),xlim=c(-1,1)) 
>>>
>>>
>>> Besides, I would like to add a reference line to the plot, but can't 
>>> find how to do that.
>>>
>>> I hope someone can give me a hint or two.
>>>
>>> Thanks in advance,
>>>
>>> Tsjerk
>>>
>>
>> Tsjerk,
>>
>> I don't think you'll get much help without knowing, first, what 
>> "strange" means, and second, what "panel.parallel.new" does. And you 
>> can always add a reference line by using panel.abline in your panel 
>> function.
>>
>> And, from the signature:
>>
>> PLEASE do read the posting guide! 
>> http://www.R-project.org/posting-guide.html
>>
>> --sundar
>>
>> ______________________________________________
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> 
> 
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