编类转化

确定要分为4类, 数据类型是ordinal data. Logit model 是用于binary variable， 就是0 或者1 的数据变量.
When the dependent variable (DV) is ordinal data, ordinal logistic regression is a method for modeling the relationship between the DV and multiple independent variables. Ordinal logistic regression is also known as ordinal regression or ordered logit models.

Ordinal logit model of y on x1 and categorical variables a and b can be written in STATA such as:

ologit y x1 i.a i.b