AttributeError: LinearRegression object has no attribute 'coef_'

Question

I've been attempting to fit this data by a Linear Regression, following a tutorial on bigdataexaminer. Everything was working fine up until this point. I imported LinearRegression from sklearn, and printed the number of coefficients just fine. This was the code before I attempted to grab the coefficients from the console.

import numpy as np
import pandas as pd
import scipy.stats as stats
import matplotlib.pyplot as plt
import sklearn
from sklearn.datasets import load_boston
from sklearn.linear_model import LinearRegression

boston = load_boston()
bos = pd.DataFrame(boston.data)
bos.columns = boston.feature_names
bos['PRICE'] = boston.target

X = bos.drop('PRICE', axis = 1)

lm = LinearRegression()

After I had all this set up I ran the following command, and it returned the proper output:

In [68]: print('Number of coefficients:', len(lm.coef_)

Number of coefficients: 13

However, now if I ever try to print this same line again, or use 'lm.coef_', it tells me coef_ isn't an attribute of LinearRegression, right after I JUST used it successfully, and I didn't touch any of the code before I tried it again.

In [70]: print('Number of coefficients:', len(lm.coef_))

Traceback (most recent call last):

 File "<ipython-input-70-5ad192630df3>", line 1, in <module>
print('Number of coefficients:', len(lm.coef_))

AttributeError: 'LinearRegression' object has no attribute 'coef_'

Answer 1

The coef_ attribute is created when the fit() method is called. Before that, it will be undefined:

>>> import numpy as np
>>> import pandas as pd
>>> from sklearn.datasets import load_boston
>>> from sklearn.linear_model import LinearRegression

>>> boston = load_boston()

>>> lm = LinearRegression()
>>> lm.coef_
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-22-975676802622> in <module>()
      7 
      8 lm = LinearRegression()
----> 9 lm.coef_

AttributeError: 'LinearRegression' object has no attribute 'coef_'

If we call fit(), the coefficients will be defined:

>>> lm.fit(boston.data, boston.target)
>>> lm.coef_
array([ -1.07170557e-01,   4.63952195e-02,   2.08602395e-02,
         2.68856140e+00,  -1.77957587e+01,   3.80475246e+00,
         7.51061703e-04,  -1.47575880e+00,   3.05655038e-01,
        -1.23293463e-02,  -9.53463555e-01,   9.39251272e-03,
        -5.25466633e-01])

My guess is that somehow you forgot to call fit() when you ran the problematic line.