[R] checking for "viability" of a GUI component

From: Hao Liu <hao.liu_at_bms.com>
Date: Wed, 30 May 2007 14:45:01 -0400

Dear All:

The question: How do I check for existance of the GUI, instead of checking the variable of the GUI?

I created a log window for several applications, they will check for the existance of log window, if it exists, append output to it, otherwise, create log window and insert to it. What I found out is that if I close the X window of the GUI, the variable logwin still exists, confuse arises to other components that are supposed to use the GUI.

create.log.win <- function(inputtext){

    if(exists(is.null("logwin"))) {return} else {

        logwin <<- tktoplevel()
        logtext <<- tktext(logwin, bg="white")
        tkwm.title(logwin," Log Window")
        loglabel <- tklabel(logwin, text="Logging Analaysis Information")
    if (is.matrix(inputtext)) {
        for (i in 1:nrow(inputtext))
            tkinsert(logtext, "end",paste(paste(inputtext[i,],collapse=" 


    else tkinsert(logtext, "end",paste(inputtext,"\n",sep=""))

        export_button <- tkbutton(logwin, text = "Export Log", command=savelog)



How do I check for existance of the GUI, instead of the variable?


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