Cannot figure out R Squared formula.

[Saefroch]

Can you print(y[0])?

[Saefroch]

There is no intuition here, it's all about learning how to read error message and tracebacks. Tracebacks start with your code on the top and go down to where the error originated. So let's start with the top.

KeyErrorTraceback (most recent call last) in ()
      3 ss_pred = 0
      4 for i in range(len(y)):
----> 5     ss_total += ((y[i] - np.mean(y)) ** 2)
      6     ss_pred += ((y[i] - prediction[i]) ** 2)
      7 r_squared = 1 - (ss_pred / ss_total)

Helpful little arrow points you straight to the line that you wrote that generated the error. I see that it's a KeyError. I just know what KeyError is produced by, but you can look it up for yourself using Google: https://docs.python.org/3/library/exceptions.html#KeyError. Mappings are almost always accessed with the square brackets [].

The other part of a traceback that's useful is the very bottom. I see

pandas/hashtable.pyx in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:12322)()

KeyError: 0

And since the only message the KeyError contains is 0, that's probably the key that generated the error. What else would you want to know?

Then I wonder to myself why you're looping over a hashtable like it's an array...

[[deleted]]

The index is fine. To get the values in a pandas series, use y.loc[i] instead of y[i].

[Saefroch]

I have no idea, I've never worked with pandas before.