Constraining parameter gradients for the test set

[mcyc]

Should we narrow the range of gradient values used for our test set? The current 1-sigma range values for temp, sigma, voff, and logN, respectively, are as the following:

LineFitting/nh3_testcubes.py

Line 78 in 17bd16a

scale = np.array([[0.2, 0.1, 0.5, 0.01]])

My biggest concern right now is the voff range. Without some sort of beam smoothing between the pixels, individual spectra in the cube can be 'velocity-incoherent' from one another if the voff gradient is larger enough. An instance of this issue can be seen in the example NH₃ (1,1) line below, where the mean spectrum of the cube is shown in grey and the central spectrum is shown in red:

[jakeown]

Well that is bad! I think we should change the line you highlighted to:
scale = np.array([[0.2, 0.1, 0.1, 0.01]])
I ran some tests with this set to 0.1 km/s and I'm not seeing these multi-peaks like we do when its at 0.2 or higher.

[mcyc]

Okay, I've implemented your suggestion in the mcyc-pgradients branch. We can merger the branch later when we have a consensus on what these values should be for our test.

[mcyc]

I've just submitted a pull request for this (see #15). @low-sky, @jpinedaf, @jakeown, and @rfriesen, feel free to make any further suggestions before the merge.