Chart scaling documentation

[jonathanolson]

In the implementation notes:

All charts automatically adjust their y-axis scale to fit the peak amplitude that is displayed. (PhET typically refers to this behavior as auto-scaling.) The exception to this is the Sum chart in the the Wave Game screen; that chart adjusts its y-axis scale to match the answer (pink waveform) but ignores the user's guess (black waveform).

It looks like there's a minimum y-axis scale of -1.5 to 1.5 on many charts (harmonics, and the Sum chart in the game as described above). Is there a way the documentation could be updated for that (unless I'm wrong)?

Review issue: #165

[pixelzoom]

You're correct -- some of the charts have a minimum y-axis scale of [-1.5,1.5]. I'll ammend implementation-notes.md.

[pixelzoom]

Revised in the above commit, here's the new paragraph:

Many of the charts automatically scale their y-axis to fit the peak amplitude, with a bit of "padding"
added to the peak. PhET typically refers to this behavior as auto-scaling. In the Discrete screen, the Sum chart auto-scales, with a minimum range of [-1.5,1.5]. In the Wave Game screen, the Sum chart auto-scales to fit the answer (pink waveform), again with a minimum range of [-1.5,1.5]. In the Wave Packet screen, all three charts auto-scale, with no minimum range.

Back to @jonathanolson for review. Feel free to close or suggest clearer language.

[pixelzoom]

Oops, revised again. Only 2 of the charts auto-scale on the Wave Packet screen. Here's the new paragraph:

Some of the charts automatically scale their y-axis to fit the peak amplitude, with a bit of "padding"
added to the peak. PhET typically refers to this behavior as auto-scaling. In the Discrete screen, the Sum chart auto-scales, with a minimum range of [-1.5,1.5]. In the Wave Game screen, the Sum chart auto-scales to fit the answer (pink waveform), again with a minimum range of [-1.5,1.5]. In the Wave Packet screen, the Amplitudes and Components charts auto-scale, with no minimum range.

[jonathanolson]

Looks great! Thanks.