[R] interactive 2-D plot interrogation

Paul Murrell p.murrell at auckland.ac.nz
Sun Feb 1 22:17:06 CET 2004


Depending on how you want the coordinates displayed, the locator() 
function may help you, or perhaps a simple function written around 
locator() to process its result into something more meaningful for your 


Dirk Eddelbuettel wrote:
> On Sun, Feb 01, 2004 at 01:53:14PM -0500, Charles Annis, P.E. wrote:
>>Greetings Friends:
>>I am trying to find a widget or some other method to let me interrogate a 
>>2-D image using the mouse.  I have a data.frame that I can visualize using
>>image() in R.  I would like to point to a pixel and have its coordinates
>>I've read Peter Dalgaard's primer on R-Tcl/Tk, R-News, 1(3):27-31, and his
>>update R-News2(3):25-27, but am still struggling. 
>>Can anyone suggest a method for interactively interrogating of a 2-D image?
> Look at the InteractiveTkrPlot example on James Wettenhall's site:
> http://bioinf.wehi.edu.au/~wettenhall/RTclTkExamples/InteractiveTkrPlot.html
> His example is over discrete set of points, which you can adapt to find the
> location with respect to curves or lines (which I did at work, where I can't
> get to right now).
> The key is that the 'widget' you bind to an event (like left-Mouse in his
> example) get (x,y) pixel coordinates from the system which given appropriate
> information from par() can be translated into your data coordinates in just
> a few steps.
> James' site is a treasure chest for R and tcltk. Highly recommended.
> Hope this helps, Dirk

Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz

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