Merge pull request #264 from alfredodeza/issue-165

add 1 to HORIZON to prevent looping errors

7-TimeSeries/2-ARIMA/README.md

@@ -224,7 +224,7 @@ Walk-forward validation is the gold standard of time series model evaluation and
     ```python
     test_shifted = test.copy()
 
-    for t in range(1, HORIZON):
+    for t in range(1, HORIZON+1):
         test_shifted['load+'+str(t)] = test_shifted['load'].shift(-t, freq='H')
 
     test_shifted = test_shifted.dropna(how='any')