[R] delete variable

[solares@unsl.edu.ar]

Why in the codigo that continues when is erased the menubutton herself is 
not erased tambien the variable one opc, though itself deberia you erase 
with the assign?  
library(tcltk)
vectPath<-c()
opc<-tclVar(init=" ")

archivos<-function(){
          f<-tkcmd("tk_getOpenFile")
          temparch<-tclvalue(f)
          assign("vectPath",c(vectPath,temparch),.GlobalEnv)
          cant<-length(vectPath)
          j<-vectPath[cant]         
          tkadd(m, "radio", label=j, variable="opc", value=j)
}

ver<-function(){ 
print(tclvalue("opc"))
}

borra<-function(){
	 assign("vectPath",c(),.GlobalEnv)
	 assign("opc"," ",.GlobalEnv)
     tkdelete(m,"0","end")
}
tt <- tktoplevel()
tkpack(mb <- tkmenubutton(tt, text="Datos"))
m <- tkmenu(mb,tearoff=FALSE) 
tkconfigure(mb,menu=m)
b<-tkbutton(tt,text="abrir",command=function()archivos())
tkpack(b)
b3<-tkbutton(tt,text="ver",command=function()ver())
tkpack(b3)
b4<-tkbutton(tt,text="Borrar",command=function()borra())
tkpack(b4)