Help on error " ValueError: For numerical factors, num_columns must be an int "

[Josef Pktd]

On Wednesday, December 16, 2015 at 9:50:35 AM UTC-5, Robert wrote:
> On Wednesday, December 16, 2015 at 6:34:21 AM UTC-5, Mark Lawrence wrote:
> > On 16/12/2015 10:44, Robert wrote:
> > > Hi,
> > >
> > > When I run the following code, there is an error:
> > >
> > > ValueError: For numerical factors, num_columns must be an int
> > >
> > >
> > > ================
> > > import numpy as np
> > > import pandas as pd
> > > from patsy import dmatrices
> > > from sklearn.linear_model import LogisticRegression
> > >
> > > X = [0.5,0.75,1.0,1.25,1.5,1.75,1.75,2.0,2.25,2.5,2.75,3.0,3.25,
> > > 3.5,4.0,4.25,4.5,4.75,5.0,5.5]
> > > y = [0,0,0,0,0,0,1,0,1,0,1,0,1,0,1,1,1,1,1,1]
> > >
> > > zipped = list(zip(X,y))
> > > df = pd.DataFrame(zipped,columns = ['study_hrs','p_or_f'])
> > >
> > > y, X = dmatrices('p_or_f ~ study_hrs', df, return_type="dataframe")
> > > =======================
> > >
> > > I have check 'df' is this type:
> > > =============
> > > type(df)
> > > Out[25]: pandas.core.frame.DataFrame
> > > =============
> > >
> > > I cannot figure out where the problem is. Can you help me?
> > > Thanks.
> > >
> > > Error message:
> > > ..........
> > >
> > >
> > > ---------------------------------------------------------------------------
> > > ValueError                                Traceback (most recent call last)
> > > C:\Users\rj\pyprj\stackoverflow_logisticregression0.py in <module>()
> > >       17 df = pd.DataFrame(zipped,columns = ['study_hrs','p_or_f'])
> > >       18
> > > ---> 19 y, X = dmatrices('p_or_f ~ study_hrs', df, return_type="dataframe")
> > >       20
> > >       21 y = np.ravel(y)
> > >
> > > C:\Users\rj\AppData\Local\Enthought\Canopy\User\lib\site-packages\patsy\highlevel.pyc in dmatrices(formula_like, data, eval_env, NA_action, return_type)
> > >      295     eval_env = EvalEnvironment.capture(eval_env, reference=1)
> > >      296     (lhs, rhs) = _do_highlevel_design(formula_like, data, eval_env,
> > > --> 297                                       NA_action, return_type)
> > >      298     if lhs.shape[1] == 0:
> > >      299         raise PatsyError("model is missing required outcome variables")
> > >
> > > C:\Users\rj\AppData\Local\Enthought\Canopy\User\lib\site-packages\patsy\highlevel.pyc in _do_highlevel_design(formula_like, data, eval_env, NA_action, return_type)
> > >      150         return iter([data])
> > >      151     design_infos = _try_incr_builders(formula_like, data_iter_maker, eval_env,
> > > --> 152                                       NA_action)
> > >      153     if design_infos is not None:
> > >      154         return build_design_matrices(design_infos, data,
> > >
> > > C:\Users\rj\AppData\Local\Enthought\Canopy\User\lib\site-packages\patsy\highlevel.pyc in _try_incr_builders(formula_like, data_iter_maker, eval_env, NA_action)
> > >       55                                       data_iter_maker,
> > >       56                                       eval_env,
> > > ---> 57                                       NA_action)
> > >       58     else:
> > >       59         return None
> > >
> > > C:\Users\rj\AppData\Local\Enthought\Canopy\User\lib\site-packages\patsy\build.pyc in design_matrix_builders(termlists, data_iter_maker, eval_env, NA_action)
> > >      704                             factor_states[factor],
> > >      705                             num_columns=num_column_counts[factor],
> > > --> 706                             categories=None)
> > >      707         else:
> > >      708             assert factor in cat_levels_contrasts
> > >
> > > C:\Users\rj\AppData\Local\Enthought\Canopy\User\lib\site-packages\patsy\design_info.pyc in __init__(self, factor, type, state, num_columns, categories)
> > >       86         if self.type == "numerical":
> > >       87             if not isinstance(num_columns, int):
> > > ---> 88                 raise ValueError("For numerical factors, num_columns "
> > >       89                                  "must be an int")
> > >       90             if categories is not None:
> > >
> > > ValueError: For numerical factors, num_columns must be an int
> > >
> > 
> > Slap the ValueError into a search engine and the first hit is 
> > https://groups.google.com/forum/#!topic/pystatsmodels/KcSzNqDxv-Q

This was fixed in patsy 0.4.1 as discussed in this statsmodels thread.
You need to upgrade patsy from 0.4.0.

AFAIR, the type checking was too strict and broke with recent numpy versions.

Josef


> > 
> > -- 
> > My fellow Pythonistas, ask not what our language can do for you, ask
> > what you can do for our language.
> > 
> > Mark Lawrence
> 
> Hi,
> I don't see a solution to my problem. I find the following demo code from 
> 
> https://patsy.readthedocs.org/en/v0.1.0/API-reference.html#patsy.dmatrix
> 
> It doesn't work either on the Canopy. Does it work on your computer?
> Thanks,
> 
> /////////////
> demo_data("a", "x", nlevels=3)
> Out[134]: 
> {'a': ['a1', 'a2', 'a3', 'a1', 'a2', 'a3'],
>  'x': array([ 1.76405235,  0.40015721,  0.97873798,  2.2408932 ,  1.86755799,
>         -0.97727788])}
> 
> mat = dmatrix("a + x", demo_data("a", "x", nlevels=3))