Python pandas: exclude rows below a certain frequency count

Question

So I have a pandas DataFrame that looks like this:

r vals    positions
1.2       1
1.8       2
2.3       1
1.8       1
2.1       3
2.0       3
1.9       1
..         


        

Answer 1

How about selecting all position rows with values >= 20

mask = df['position'] >= 20
sel = df.ix[mask, :]