I've established by trial and error, (inconsistently) that the Major Unit (for the x-axis)
determines the intervals between the ticks on the x-axis. Base Units determines
the interval between plotted points, but the significance of Minor Units eludes
me; morevover, ticks in the check boxes for the (3) Units seem to make no
difference. Can someone clear up my befuddlement please ? HELP can't
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