plotTS() docs unclear on skipping the isopycnals

[dankelley]

A user might want to skip the drawing of isopycnals, but I don't see in the documentation that this is provided. You can get this by doing e.g.

plotTS(..., levels=NULL)

I think the same effect should occur for nlevels=0, but when I try that, I get some isopycnals.

I will look into this later today or tomorrow. I also plan to add a few lines to the docs to explain how a person might do things like add isopycnals themselves, or add other things, e.g. spiciness, sound speed, etc.

[dankelley]

I've fixed this in "develop" commit 2730750e5647126a38af283d3866dbd9057becfc. Now, you can turn off isopycnals with two schemes

plotTS(..., nlevel=0) # method 1
plotTS(..., levels=NULL) # method 2

and this is documented.

Plus, added a thing to the docs to show how to add spice contours. I guess we could get a new function parameter for that, but I prefer showing users how to do it, because then then users learn how to customize things as they wish. For example, they might want to show sigma1 instead of the sigma0 that is shown by default.