[R-gui] How are Code Generated Names implemented in R tcltk

[James Wettenhall]

Hi Bill,

> Hello R tcltk world:
> After a month without success, I seek help.  Perhaps one of you has the
> knowledge to construct a checkbutton for each element of vector of
> variable length, select any combination of buttons, and then output the
> vector of selected buttons.  The following code does not work:

Here's some code I threw together pretty quickly which I think does what
you are asking for.  You may find a more elegant way.

Best wishes,
James

####################################################
Selected <- c()
library(tcltk)
Buttons <- c(2,5,7)
tt <- tktoplevel()
ButtonWidget <- list()
ButtonVar <- list()
for(i in 1:3) {
  ButtonName <- paste("B", Buttons[i], sep="")
  ButtonWidget[[i]] <- tkcheckbutton(tt)
  ButtonVar[[i]] <- tclVar("0")
  tkconfigure(ButtonWidget[[i]],text=ButtonName,
              variable=ButtonVar[[i]],indicatoron=0)
  tkpack(ButtonWidget[[i]])
}


OK <- tkbutton(tt,text="  OK  ", command=function() {
  Selected <<- c()
  for(i in 1:3)
    if(tclvalue(ButtonVar[[i]]) == "1")
      Selected  <<- c(Selected, Buttons[i])
    cat(paste(Selected,collapse=","))
    cat("\n")})
tkpack(OK)
####################################################

>
> require(tcltk)
> Buttons <- c(2,5,7)
> tt <- tktoplevel()
> for(i in 1:3) {
>   ButtonName <- as.name(paste("B", Buttons[i], sep=""))
>   ButtonName <- tkcheckbutton(tt)
>   ButtonValue <- as.name(paste("B", Buttons[i], "Value", sep=""))
>   ButtonValue <- tclVar("0")
>   tkconfigure(ButtonName, text=paste(Buttons[i]), variable=ButtonValue,
> indicatoron=0)
>   tkpack(ButtonName)
> }
> OK <- tkbutton(tt,text="OK", command=function() { for(i in 1:3) {
>   if(as.character(tclvalue(paste("B",Buttons[i],"Value", sep=""))) == "1")
> Selected <<- c(Selected, Buttons[i])}} )
> tkpack(OK)
> Selecting any combination of checkbuttons results in the message "Error in
> structure(.External("dotTclObjv", objv, PACKAGE = "tcltk"), class =
> "tclObj") : [tcl] can't read "B2Value": no such variable."  When the
> evaluated results of as.name ... are entered interactively in place of the
> loop with ButtonName and ButtonValue variables, the mini GUI works.  How
> would checkbutton names and checkbutton variable values generated in a
> loop be correctly implemented?
> Thanks,
> Bill Morphet, Space shuttle analyst/USU PhD statistics student
>
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>
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