[R] Maps and plotting

Barry Rowlingson B.Rowlingson at lancaster.ac.uk
Thu Oct 14 12:42:13 CEST 2004

Shawn Way wrote:
>  At our facility we have multiple sample points that are sampled on any
> given day.  What I would like to do is create a map of the facility with
> the sample points (and point labels) and when we have out of
> specification results, place a transparent dot over the area on the map.
> As the number of OOS results builds up, I envision the dot getting
> darker.

  Over what timescale? This sounds like it could be an interactive, 
real-time on-line monitoring thing. Is it?

  In which case R's graphics devices might not be good enough, and you'd 
be better off using a TclTk graphics canvas.

  library(tcltk) and read the docs!

  Another idea, if all you are doing is updating a daily image, would be 
to use a language like Python, and the Python Imaging Library (PIL) to 
draw pretty graphs.

  I've done something similar that produces daily maps of disease 
incidence, but I used different size and colour circles and not 
transparency, so I just used base R graphics and produced a PNG file. If 
I wanted transparency I'd probably use Python/PIL, which can handle 
alpha channels.


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