[R] identify() and postscript output

David Winsemius dwinsemius at comcast.net
Thu Mar 5 15:59:12 CET 2009

 From the help page:
identify is a generic function, and only the default method is  
described here.

identify is only supported on screen devices such as X11, windows and  
quartz. On other devices the call will do nothing."

Why not collect the specifics of the identified points and then replot  
to your chosen output device perhaps with a different color or a text  
label? identify should return a value that can be used for that  
purpose. The help page provides an example that should be modifiable  
for that purpose.


David Winsemius

On Mar 5, 2009, at 9:18 AM, Michael Friendly wrote:

> In the following, I'm fitting a logistic regression model, and using  
> car:::influencePlot.  When I run the latter with
> output to the screen, it calls identify() that lets me label  
> observations with large CookD.
> However, if I use postscript() to get .eps output, identify() seems  
> not to be called at all.  If instead, I
> use dev.copy2eps() after getting output to the screen, the point  
> labels do not appear in the resulting .eps
> graph.  Why?  Is there a workaround?
> library(vcd)
> data(Arthritis)
> # define Better
> Arthritis$Better <- Arthritis$Improved > 'None'
> arth.mod1 <- glm(Better ~ Age + Sex + Treatment , data=Arthritis,  
> family='binomial')
> library(car)
> # influence plot
> #postscript(file="arthritis-diag2.eps", paper="special", height=6,  
> width=6, onefile=TRUE, horizontal=FALSE)
> influencePlot(arth.mod1, main="Arthritis data: influencePlot")
> #dev.off()
> -Michael
> -- 
> Michael Friendly     Email: friendly AT yorku DOT ca Professor,  
> Psychology Dept.
> York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
> 4700 Keele Street    http://www.math.yorku.ca/SCS/friendly.html
> Toronto, ONT  M3J 1P3 CANADA
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