SetMarginsPixels — Set margins around the plot area
$plot->SetMarginsPixels($lm,$rm,$tm,$bm)
SetMarginsPixels sets the margins around the plot area,
overriding the automatic margin size calculation.
The four margins are specified independently and in pixels.
$lmThe left margin, in pixels.
$rmThe right margin, in pixels.
$tmThe top margin, in pixels.
$bmThe bottom margin, in pixels.
By default, the margin sizes are automatically calculated based on the amount of room needed (for the axis labels, tick labels, and tick marks).
The upper left corner of the plot area is at device coordinates (Left_Margin, Top_Margin). The lower right corner of the plot area is at device coordinates (Image_Width - Right_Margin, Image_Height - Bottom_Margin).
Calling SetMarginsPixels causes PHPlot to forget
a plot area set with SetPlotAreaPixels.