[lupire]

If 0 is not useful reference, then the chart should have the X axis on top, to avoid the intuitive tendency to interpret the graph as a heigh chart.

[function_seven]

That’s too weird for most audiences. Removing the X axis altogether seems more appropriate (while keeping the labels). Then the plot area is still “bottomless” in a sense, but the labels are where people expect to see them.

Having the axis on top implies that the values are negative. Like an ocean depth chart.