Dear list,

I have the following to Pandas Series: a, b. I want to slice and then subtract. Like this: a[1:4] - b[0:3]. Why does it give me NaN? But it works in Numpy.

Example 1: did not work

>>>a = pd.Series([85, 86, 87, 86])

>>>b = pd.Series([15, 72, 2, 3])

>>> a[1:4]-b[0:3]
0 NaN
1 14.0
2 85.0
3 NaN

>>> type(a[1:4])

<class 'pandas.core.series.Series'>

Example 2: worked

If I use values() method, it's converted to a Numpy object. And it works!

>>> a.values[1:4]-b.values[0:3]

array([71, 15, 84])

>>> type(a.values[1:4])

<class 'numpy.ndarray'>

What's the reason that Pandas in example 1 did not work? Isn't Numpy built on top of Pandas? So, why is everything ok in Numpy, but not in Pandas?

Thanks in advance!