The mnlogit package in R allows for the fast estimation of multinomial logit models.The specification of forumlas is a bit different from most other regression models/packages in R, however. Using the Fish dataset as a reproducible example, > require(mnlogit)Loading required package: mnlogitPackage: mnlogitVersion: 1.1.1Multinomial Logit Choice Models.Scientific Computing Group, Sentrana Inc, 2013.> data(Fish, package ='mnlogit')> head(Fish)           mode   income     alt   price  catch chid1.beach   FALSE 7083.332   beach 157.930 0.0678    11.boat    FALSE 7083.332    boat 157.930 0.2601    11.charter  TRUE 7083.332 charter 182.930 0.5391    11.pier    FALSE 7083.332    pier 157.930 0.0503    12.beach   FALSE 1250.000   beach  15.114 0.1049    22.boat    FALSE 1250.000    boat  10.534 0.1574    2I'm trying to understand the difference between the model specification of fm <- formula(mode ~ 0 + price | income | catch)andfm <- formula(mode ~ 0 + price | income + catch)while the documentation covers the detail of such changes  in the general coeffcient area of the forumla (i.e. where price is), I don't see an explanation of how operators like + affect the alternative-specific area of the formula/code, relative to |.
How to Interpret Multinomial Specification in R's `mnlogit` package
r;logistic regression;regression