title: R gwidgets: Dynamic update of gcheckboxgroup with change in gcombobox input
body: <p>I am using gcombobox to select the input and populating checkbox dynamically and it's working properly but when I am selecting second input it's not clearing the first output(checkbox) and appending on first one ending up two checkbox and so on..
  Is there a way to clear the first input or reflect only one checkbox at one time?</p>
  
  <p>Below is the piece of code-</p>
  
  <pre><code>datanames&lt;- c("mydata","yourdata")
  f&lt;-function(h,...) 
   {   
  x&lt;-(data.frame(get(svalue(h$obj)))) 
      xy&lt;&lt;-names(x)
  
      ab&lt;-gcheckboxgroup(xy,checked = FALSE,
                      handler = function(h,...) s&lt;&lt;-(svalue(h$obj)),expand=TRUE, container = gf2,use.table=TRUE)
  }
  w&lt;-gwindow("action")
  gp&lt;-ggroup(horizontal=F,container=w)
  gf1 = gframe(text="INPUT",cont=w,container=gp)
  gf2 = gframe(text="SELECT",cont=w)
  cb&lt;-gcombobox(datanames,container=gf1,handler=f,expand=TRUE)
  </code></pre>
  
  <p>I don't know how to clear the gcheckboxgroup with change in gcombobox input.</p>
  
  <p>Thanks!
  Om</p>