I would like to write a GUI (preferably starts in Windows) for a R package. Do you have any suggestions where to start from? Do you have any package or softwares for that?
I have to mention that I do not know whether making an interface between R and MATLAB is possible or not but it would be easy to implement if 'R' can be called from MATLAB (by making an interface between R and MATLAB, I mean). In this case, you can write an mfile including R call from MATLAB and then easily use it as an executive function in the form of GUI.
Meanwhile, I recommend you purchase the following educational DVD about GUI (in Persian).
You could also implement your GUI in any environment you prefer (such as java or visual c++) and call you R-script from that GUI by executing RScript. See: http://stat.ethz.ch/R-manual/R-devel/library/utils/html/Rscript.html