enhancement . applyeval
df = P.DataFrame({'a':[1,1,2,2,3,3], 'b':range(6)})

How about a function  applyeval

df.groupby('a').applyeval( "b/b.mean()" )

instead of:

df.groupby('a').apply( lambda x: x.eval( "b/b.mean()" ))

Thank you
Gla
