Binary operations on int DataMatrix
Reported by kwgoodman, Jun 12, 2010
When adding two int DataMatrix's a ValueError is raised when matrix.py attempt to fill missing values with NaN:

> > dma1 = pandas.DataMatrix([[1, 2], [3, 4]], ['a', 'b'], ['c', 'd'])
> > dma2 = pandas.DataMatrix([[1, 2], [3, 4]], ['b', 'a'], ['d', 'c']) 
> > dma1 + dma2
> > <snip>
> > ValueError: cannot convert float NaN to integer

Delete comment Comment 1 by kwgoodman, Jun 12, 2010
Possible fix:

> > x = np.array([1.0])
> > issubclass(x.dtype.type, np.inexact)
> >    True
> > x = np.array([1])
> > issubclass(x.dtype.type, np.inexact)
> >    False
> > x = np.array([1.0], dtype=object)
> > issubclass(x.dtype.type, np.inexact)
> >    False
> > x = np.array([1.0], dtype=str)
> > issubclass(x.dtype.type, np.inexact)
> >    False
