stats model OLS question/issue

[scidam]

Its not really relevant to my problem, but do you know why it would work when using matplotlib module and not with the statsmodels module?

There is no magic with - character, it is just one character of a string. Statsmodels internally parses the formula given. It looks for +, ~ and - symbols in a string representing the formula. When statsmodels find -, it treats surrounding alphanumeric substrings C and IC_6MU as factor/column names (but your data frame doesn't have such columns). All this behavior is implemented in statsmodels to get it closer to R-like (formula) syntax.
When you call plt.plot(chem_film_data_df['C-IC_6MU'], chem_film_data_df['pass_fail'],'o'), only pandas selection
engine works: you get chem_film_data_df['C-IC_6MU'] and chem_film_data_df['pass_fail'] which are iterables (Pandas.Series instances); and these iterables are passed to the plot function.


When AFAIK, Matplotlib doesn't perform similar parsing. How