SetPrintImage — Determine whether or not to automatically output the image when the plot is drawn
$plot->SetPrintImage($pi)
SetPrintImage determines whether or not to automatically
output the image (as if PrintImage was used) when a plot
is drawn (with DrawGraph). The default is True.
When putting multiple plots on one image, is is necessary to defer PrintImage
until after all the plots have been drawn.
$piTrue to automatically print the image when drawn with DrawGraph; False to defer printing the image until PrintImage is explicitly called.
See Section 4.6, “Multiple Plots Per Image” for more information on putting multiple plots on an image.