A question about "plot recorder" command!

[foadEng]

Hi
I have a question about "plot recorder" command :

recorder plot $fileName $windowTitle $xLoc $yLoc $xPixels $yPixels -columns
$xCol0 $yCol0 <-columns $xCol1 $yCol1><-columns $xCol2 $yCol2> ...

I can't understand what we should put instead of $xCol0 & $yCol0 parameters! I have read the manual but I couldn't understand. The manual says that these are column number to be plotted in X-axis and Y-axis. But what does "column number" means here?! Is it the element number or something else?!
Also it says that "One set of columns must be defined". what does "One set of columns" mean?

Thank you very much

[fmk]

the output file can be considered a matrix, with a column for every bit of info being recorded and a row for each time the recorder is asked to record xCol0 and yCol0 are the two columns of the matrix that you wish to plot. if the file contains 2 columns, 1 and 2 would be what you provide.