SetDrawXGrid — Whether or not to draw the X grid lines
$plot->SetDrawXGrid($dxg
)
SetDrawXGrid
enables or disables the drawing of the X
grid lines. (The X grid lines are the vertical lines which intersect the
X axis and are parallel to the Y axis.)
The default is to not draw the X grid for vertical plots,
and to draw the X grid for horizontal plots.
Grid lines are drawn at tick mark positions.
SetLightGridColor sets the color of the grid lines.