[R] Mass 'identify' on 2d-plot

[Duncan Temple Lang]

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Barry Rowlingson wrote:
> Evgeniy Kachalin wrote:
> 
> 
>>What is ability in R to graphically (per mouse) define some area and to 
>>select all the cases felt in it?
>>
>>'identify' is OK for 5-10 cases, but what if cases=1000?
> 
> 
>   You can use 'locator' to let the user click a number of points to 
> define a polygon, and then use one of the point-in-polygon functions 
> provided by one of the spatial packages to work out whats in your polygon.
> 
>   Look at splancs, spatstat, sp - pretty much anything beginning with 
> 'sp' - on CRAN.
> 
>   In splancs you can just do:
> 
>   poly = getpoly()
> 
>   - which lets the user draw a polygon on screen, then:
> 
>   inPoly = inpip(xypts,poly)
>   points(xypts[inpip,], pch=19,col="red")
> 
>   and that will plot the selected points in solid red dots.
> 
>   I don't think there's a way to draw a freehand figure on an R plot, 
> you have to go click, click, click, and draw straight lines.


FWIW, there is an "experimental" package on the
Omegahat site (and repository) named

   RGtkIPrimitives

that works with the gtkDevice only to do
rubber banding and free form region identification.


> 
> Barry
> 
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- --
Duncan Temple Lang                duncan at wald.ucdavis.edu
Department of Statistics          work:  (530) 752-4782
371 Kerr Hall                     fax:   (530) 752-7099
One Shields Ave.
University of California at Davis
Davis, CA 95616, USA
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