title: StatsModels not aligned Error
body: <p>I am getting an error when I try to run a multivariable linear regression in Statsmodels.  Everything works fine when I hardcode just one X column in the XData variable.</p>
  
  <p>Can someone please give me some advice as what I'm missing here?  I would greatly appreciate it.</p>
  
  <p>Error:</p>
  
  <p>ValueError: shapes (747,2) and (747,2) not aligned: 2 (dim 1) != 747 (dim 0)</p>
  
  <p>Code:</p>
  
  <pre><code>import pandas as pd
  import statsmodels.api as sm
  import itertools
  
  data = pd.read_csv("deaconFoodData.csv")
  
  for i in range(2,10,1):
      xCombinations = itertools.combinations(["Food Exp","HH Size","HH Inc","Highest Ed Head","Age Head","Shopping Time","Kid &lt;6","Kid 6-18","Eating Healthy"], i)
      print(str(i) + " variables")
      for combination in xCombinations:
  
          comb = list(combination)
  
          print(comb)
          xData = data[["Food Exp", "HH Size"]] # data[comb]
          yData = data["Shopping LH"]
          yData = sm.add_constant(yData, prepend=False)
          print(yData)
          # Fit and summarize OLS model
          mod = sm.OLS(xData, yData)
          res = mod.fit()
          print(res.rsquared)
  </code></pre>
  
  <p>GitHub Link:
  <a href="https://github.com/deacons2016/DeaconFood" rel="noreferrer">https://github.com/deacons2016/DeaconFood</a></p>