Unpack Java jars

Apparently java files are archives! Laut Extracting the Contents of a JAR File (The Java™ Tutorials > Deployment > Packaging Programs in JAR Files) it’s jar xf jar-file [archived-file(s) to extract].

Pandas and numpy have different std/stdev standard deviation functions!

Both are correct, one divides by N, the other by N-1.

t df.std()==np.std(df, ddof=1). Somethingsomething delta degrees of freedom. ddof=0 can also be passed to pandas.