User reported issue: Harmonics and Sum graphs disappear when all coefficients are zero

[oliver-phet]

In the “Fourier: Making Waves” app, when all coefficients are zero, the “Harmonics” and “Sum” graphs disappear, when they should remain visible as a horizontal line since the sum still exists (bust is zero for all positions / times).

@arouinfar replied: Can you please open an issue?

The user is technically correct, an amplitude of zero results in a line at y=0. If we display these in the Harmonics graph, all of the zero terms would obscure one another, but hovering over the amplitude slider brings that term to the front. Likewise, if all harmonic amplitudes are zero, the sum would display a line at y=0. We do not display these y=0 lines because they muddy up the display, and adding zero doesn't do anything. If we want to support this request, I would suggest creating a Preference to display the y=0 lines that defaults to false.

[arouinfar]

We can consider this request for the next release, but for now I'm going to unassign myself.

[pixelzoom]

This issue is not in scope for #247 (1.1 release) because it is a problem that is present in the published version, and would take significant design & development resources to address.