Rolling mean, returning nan in dataframe pandas python
<p>So I have been trying to work out the moving average, and when outputed it gives me <code>NaN</code> for some reason</p>

<pre><code>import pandas as pd
import pandas_datareader.data as web
import numpy as np
currentTime = datetime.now().date()

f = web.DataReader('goog', 'yahoo', start=2014-1-1, end=currentTime)
ma_50 = pd.rolling_mean(f, window=50)
print(ma_50)
</code></pre>

<p>The output just gives me date and the value that i want appears to be <code>NaN</code> like this:</p>

<pre><code>2012-01-03         NaN         NaN         NaN         NaN        NaN   
</code></pre>