Update "Differences between R and Patsy Formulas" to state that dot on RHS is not supported #134

Activity

1. steve-the-bayesian commented on Dec 25, 2019

   

   steve-the-bayesian

   on Dec 25, 2019

   More actions

   Here is some somewhat clunky code that can handle most of what the dot operator in R can do (albeit not as gracefully). I agree that the absence of '.' is a fairly large omission from the formula language.

   `def dot(data_frame, omit=[]):
   """

   Build a formula string by "summing" all entries except those on an 'omit
   list'.  This would typically include the name of the variable on the left
   hand side of the equation.
   
   This function is named for the 'dot' operator in R, where a formula given
   as 'y ~ .' means "regress y on all other variables".  The R dot operator
   can also be used to specify interactions, as in y ~ .^2.  To allow for
   similar specifications, the return value of this function is wrapped in
   paraentheses "()".
   
   Args:
   
     data_frame: The data frame from which to build the equation.  A list or
       array of column names is also acceptable.
   
     omit:  A list of names to omit.
   
   Returns:
     A string containing the list of names in data_frame, separated by '+'.
     The return value begins with '(' and ends with ')' so that y~dot(data,
     omit=["y"])**2 can be used to specify all 2-way interactions.
   
   """
   vnames = [x for x in data_frame.columns if x not in omit]
   ans = "(" + "+".join(x for x in vnames) + ")"
   return ans
   

   `