stats model OLS question/issue

[russoj5]

Good Afternoon All,

I am a newbie with Python and coding and trying to model something. I am importing a CSV file and trying to use the OLS function to run a linear regression model. This is the code I'm using:

import numpy as np

import matplotlib.pyplot as plt

import pandas as pd

import scipy as sp

import statsmodels.formula.api as smf

import sys

from IPython.display import display, HTML

 

 

print(sys.path)

 

chem_film_data_df = pd.read_csv (r"chem_film_data.csv")

columns_to_keep = ['Date', 'pass_fail', 'C-IC_6MU', 'Nitric_Acid', 'Etch_Rate']

chem_film_data_df = chem_film_data_df[columns_to_keep]

print(chem_film_data_df)

 

display(HTML(chem_film_data_df.head().to_html()))

 

print("Number of rows in the dataset =", len(chem_film_data_df))

 

#plt.plot(chem_film_data_df['C-IC_6MU'], chem_film_data_df['pass_fail'],'o')

#plt.title('Test', fontsize=20)

#plt.xlabel('C-IC 6MU Test')

#plt.ylabel('pass-fail test')

#plt.show()

 

chem_film_model = smf.ols("pass_fail ~ C-IC_6MU + Nitric_Acid + Etch_Rate", chem_film_data_df).fit()

print(chem_film_model.summary())

I've added a few lines of code that allowed me to verify that it was importing the correct information from the CSV, which it is, but when it gets to line 27 it outputs an error. The commented out code was a test I ran to verify that data from the CSV was being imported and I was able to use it.

The test output is correct:

Output:
['C:\\Users\\JA21877\\Desktop\\python', 'C:\\Program Files\\Python38\\python38.zip', 'C:\\Program Files\\Python38\\DLLs', 'C:\\Program Files\\Python38\\lib', 'C:\\Program Files\\Python38', 'C:\\Users\\JA21877\\AppData\\Roaming\\Python\\Python38\\site-packages', 'C:\\Users\\JA21877\\AppData\\Roaming\\Python\\Python38\\site-packages\\win32', 'C:\\Users\\JA21877\\AppData\\Roaming\\Python\\Python38\\site-packages\\win32\\lib', 'C:\\Users\\JA21877\\AppData\\Roaming\\Python\\Python38\\site-packages\\Pythonwin', 'C:\\Program Files\\Python38\\lib\\site-packages', 'C:\\Users\\JA21877\\AppData\\Roaming\\Python\\Python38\\site-packages\\IPython\\extensions']

          Date  pass_fail  C-IC_6MU  Nitric_Acid  Etch_Rate

0    10/1/2018          1    5.9050       87.191   0.309628

1    10/4/2018          1    5.9050       87.191   0.309628

2    10/4/2018          1    5.9050       87.191   0.354437

3    10/4/2018          1    5.9050       87.191   0.222378

4    10/4/2018          1    5.9050       87.191   0.133427

..         ...        ...       ...          ...        ...

220  7/13/2020          1    5.9710       91.839   0.211808

221  7/17/2020          1    6.0131       92.466   0.235234

222  7/22/2020          1    6.4769       94.186   0.342308

223  7/24/2020          1    6.4777       88.799   0.316139

224  7/29/2020          1    6.4337       94.687   0.314921

 

[225 rows x 5 columns]

<IPython.core.display.HTML object>

Number of rows in the dataset = 225

But then I receive this message:

Error:
Traceback (most recent call last):

  File "C:\Users\JA21877\Desktop\python\chem_film_predictive_model.py", line 27, in <module>

    chem_film_model = smf.ols("pass_fail ~ C-IC_6MU + Nitric_Acid + Etch_Rate", chem_film_data_df).fit()

  File "C:\Users\JA21877\AppData\Roaming\Python\Python38\site-packages\statsmodels\base\model.py", line 168, in from_formula

    tmp = handle_formula_data(data, None, formula, depth=eval_env,

  File "C:\Users\JA21877\AppData\Roaming\Python\Python38\site-packages\statsmodels\formula\formulatools.py", line 64, in handle_formula_data

    result = dmatrices(formula, Y, depth, return_type='dataframe',

  File "C:\Users\JA21877\AppData\Roaming\Python\Python38\site-packages\patsy\highlevel.py", line 309, in dmatrices

    (lhs, rhs) = _do_highlevel_design(formula_like, data, eval_env,

  File "C:\Users\JA21877\AppData\Roaming\Python\Python38\site-packages\patsy\highlevel.py", line 167, in _do_highlevel_design

    return build_design_matrices(design_infos, data,

  File "C:\Users\JA21877\AppData\Roaming\Python\Python38\site-packages\patsy\build.py", line 893, in build_design_matrices

    rows_checker.check(value.shape[0], name, origin)

  File "C:\Users\JA21877\AppData\Roaming\Python\Python38\site-packages\patsy\build.py", line 795, in check

    raise PatsyError(msg, origin)

patsy.PatsyError: Number of rows mismatch between data argument and C (225 versus 1)

    pass_fail ~ C-IC_6MU + Nitric_Acid + Etch_Rate

                ^

[Finished in 3.1s]

Any idea what is going on? I'm not sure why its saying there is a row mismatch, when the output of the rows/columns shows they are the same. Thank you in advance for your help!