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The plot is not empty. If you look carefully you will see a blue line stuck along the axes.

The function h is a quotient of two functions, and the denominator has zeros on the plotting interval.

This means the function h takes immense values.

Because of this, the scale chosen for y is immense, which is sadly not reflected in the tick labels.

The tick labels look like 0.5 to 4.0, but they are probably something like 0.5e100 to 4.0e100 but being too large they do not display properly.

The solution is to set the plotting window by choosing an appropriate ymin and ymax.

Additionally you can use detect_poles=True to get rid of spurious vertical lines when the function jumps from minus infinity to plus infinity.

Depending on the scale you choose, try something like:

sage: ph = plot(h, (0, 10), detect_poles=True)

sage: ph.show(ymin=-100, ymax=100)
Launched png viewer for Graphics object consisting of 3 graphics primitives

sage: ph.show(ymin=-10, ymax=10)
Launched png viewer for Graphics object consisting of 3 graphics primitives

sage: ph.show(ymin=-1, ymax=1)
Launched png viewer for Graphics object consisting of 3 graphics primitives


The plot is not empty. If you look carefully you will see a blue line stuck along the axes.

The function h is a quotient of two functions, and the denominator has zeros on the plotting interval.

This means the function h takes immense values.

Because of this, the scale chosen for y is immense, which is sadly not reflected in the tick labels.

The tick labels labels, which look like 0.5 to 4.0, 4.0, are really 0.5e6 to 4.0e6, but they are probably something like 0.5e100 to 4.0e100 but being too large they for some reason do not display properly.

Check this:

sage: ph = plot(h, (0, 10))

sage: ph.get_minmax_data()
{'xmin': 0.0005025125628140704,
'xmax': 10.0,
'ymin': -102.31864962768964,
'ymax': 3960099.7499999963}


The solution is to set the plotting window by choosing show an appropriate view by setting ymin and ymax.

Additionally you can use detect_poles=True to get rid of spurious rid of spurious vertical lines when the function jumps from from minus infinity to plus infinity.

Depending on the scale you choose, try something like:

sage: ph = plot(h, (0, 10), detect_poles=True)

sage: ph.show(ymin=-100, ymax=100)
Launched png viewer for Graphics object consisting of 3 graphics primitives

sage: ph.show(ymin=-10, ymax=10)
Launched png viewer for Graphics object consisting of 3 graphics primitives

sage: ph.show(ymin=-1, ymax=1)
Launched png viewer for Graphics object consisting of 3 graphics primitives