Exercises from Hogg's paper
fit_straight_line.py fits a straight line to data using least-squares.
myemcee.py is an almost line for line copy of Dan's emcee example at http://dan.iel.fm/emcee/current/user/line/
mcmc_line.py uses emcee to fit a straight line to data.
mixture_model.py implements the mixture model from exercise 6.