Add leading (1,0)?

[j-tweed]

By definition proportional mass remaining should be 1 at time 0. Should litterFitter [optionally?silently?] add this value on if it finds it is missing from the data?

[wcornwell]

Seems like there are three options:

1. Fix the line through (1,0). Some of the curves do this (e.g. negative exponential) by the way they're written down. This assumes no error in the initial mass estimate, which is not totally true, but I think it's defensible as a pragmatic choice.
2. Add (1,0) and treat it like all other points
3. Don't add it, and let the curve fit do whatever it wants

This seems like a good option to add to litterFitter

[j-tweed]

having slept on it, I think it is best not to include a (0,1) in the dataset, as it may mess with the statistical fitting. I feel like the (0,1) is already implicit in the calculation of all the proportional mass values, so adding a point is an unwarranted extra degree of freedom.

I would be happy if plot.litterFit() just set the ylim to (0,1) - so that you always see the (0,1) point in the default plots. But yes, allowing the user to specify options 1-3 above might also be handy.