xtape - set up the record process of graphics
xtape is used to set up the record process of graphics:
xtape("on") just selects the driver "Rec" which records all the graphics operations.
xtape("clear",num) clears the graphics window num and clears the recorded graphics associated with window num.
xtape("replay",num) redisplays all the recorded graphics in the window num.
xtape("replaysc",num,rect) replots the graphics window num using rect=[xmin,ymin,xmax,ymax] as x and y bounds.