[R] Equal confidence interval arrowhead lengths across multiple-paneled lattice plots with free y-scales

[Bob Farmer]

Yep, that did it, thanks.

--Bob

Deepayan Sarkar wrote:
> On Nov 15, 2007 8:08 PM, Bob Farmer <farmerb at gmail.com> wrote:
>> Hi.
>> I've got a lattice plot with multiple panels and two groups superimposed
>> on each panel.  Each panel has an independently scaled y-axis (scales =
>> list(relation = "free")).
>>
>> I've successfully put up 95%CI error bars using panel.arrows (and some
>> help from the mailing list).  My question is whether I can "unscale" the
>> arrowheads so that they appear to have the same length across all panels.
>> I recognize from the help-file that the "length" argument in
>> panel.arrows is in terms of grid units (which I assume are specific to
>> the particular panel).  Can anybody think of a way to set the length so
>> that it appears uniform across all panels?
> 
> The obvious approach would be to use a relative unit like "cm" or
> "inch" instead of an absolute one like "native". Does that not work?
> 
> -Deepayan
> 
>> Example code:
>>
>>    summTable<-data.frame("X" = seq(1,12), "Y" =
>> c(1,8,3,6,6,5,7,3,8,1,10,-2),
>>      "Location" = rep(c("Site1", "Site2"), times = c(6,6)),
>>      "Species" = rep(c("A", "B"), 6)
>>      )
>>
>> #change scale for Site 1
>>    summTable[1:6,2]<-100*summTable[1:6,2]
>>
>> #arbitrary confidence intervals
>>    summTable<-cbind(summTable, "ly" = (summTable$Y*(.98)),
>>      "uy" = (summTable$Y*1.02)
>>      )
>>
>> #panel plotting
>>    panel.func<-function(x,y,ly,uy,subscripts,...){
>>      ly<-as.numeric(ly)[subscripts]
>>      uy<-as.numeric(uy)[subscripts]
>>      panel.arrows(x,ly,x,uy,
>>        unit = "native",
>>        angle = 90,
>>        length = .25,
>>        code = 3,
>>        )
>>      panel.xyplot(x,y,...)
>>      }
>>    xyplot(Y ~ X | Location, groups = Species,
>>      type = "l",
>>      data = summTable,
>>      scales = list(relation = "free"),
>>      ly = summTable$ly, uy = summTable$uy,
>>      auto.key = T,
>>      panel = panel.superpose,
>>      panel.groups = panel.func
>>      )
>>
>> Thank you.
>>
>> --Bob Farmer
>> (using R 2.6.0 and lattice 0.16-5)
>>
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>>
>