            ^
         invalid set option.

Set options which GnuPlot+ recognises are: [] = choose one, <> = optional

'arrow', 'autoscale', 'data style', 'function style', 'grid', 'key', 'label',
'linestyle', 'log', 'noarrow', 'nogrid', 'nokey', 'nolabel', 'nolinestyle',
'nolog', 'pointsize', 'samples', 'terminal', 'title', 'width',
'[xyz]<n>label', '[xyz]<n>range'

Set options from GnuPlot which GnuPlot+ DOES NOT recognise:

'angles', 'bars', 'border', 'boxwidth', 'clabel', 'clip', 'cntrparam',
'colorbox', 'contour', 'decimalsign', 'dgrid3d', 'dummy', 'encoding',
'format', 'hidden3d', 'historysize', 'isosamples', 'locale', '[blrt]margin',
'mapping', 'mouse', 'multiplot', 'offsets', 'origin', 'palette', 'parametric',
'pm3d', 'polar', 'print', '[rtuv]range', 'size', 'style', 'surface', 'tics',
'ticscale', 'ticslevel', 'timestamp', 'timefmt', 'view', '[xyz]{2}data',
'{no}{m}[xyz]{2}tics', '[xyz]{2}[md]tics', '{[xyz]{2}}zeroaxis', 'zero'

