Give Scott's pi and Bennett's S options

[kayaulai]

Scott's pi: Pool together the category estimates for the two raters
Bennett's S: Just treat the categories as equal probability
Modified Bennett's S: Treat non-zero boundaries as equal probability

[kayaulai]

with speaker_num, add a parameter

• metric
• by default, it is "kappa", but also add options "pi", "s", "s_modfieid"

also change the name of the function to getDistributionsFromAnno