BUG: rolling functions raise ValueError on float32 data

[jennolsen84]

pd version: v0.18.0rc1

minimal example:

import pandas as pd
import numpy as np
pd.DataFrame(np.arange(5, dtype=np.float32)).rolling(window=3).max()

stack trace:

<ipython-input-25-795ba6485799> in <module>()
----> 1 pd.DataFrame(np.arange(5, dtype=np.float32)).rolling(window=3).max()

/venv/lib/python3.4/site-packages/pandas/core/window.py in max(self, **kwargs)
    767     @Appender(_shared_docs['max'])
    768     def max(self, **kwargs):
--> 769         return super(Rolling, self).max(**kwargs)
    770 
    771     @Substitution(name='rolling')

/venv/lib/python3.4/site-packages/pandas/core/window.py in max(self, how, **kwargs)
    541         if self.freq is not None and how is None:
    542             how = 'max'
--> 543         return self._apply('roll_max', how=how, **kwargs)
    544 
    545     _shared_docs['min'] = dedent("""

/venv/lib/python3.4/site-packages/pandas/core/window.py in _apply(self, func, window, center, check_minp, how, **kwargs)
    474 
    475             if values.ndim > 1:
--> 476                 result = np.apply_along_axis(calc, self.axis, values)
    477             else:
    478                 result = calc(values)

/venv/lib/python3.4/site-packages/numpy/lib/shape_base.py in apply_along_axis(func1d, axis, arr, *args, **kwargs)
     89     outshape = asarray(arr.shape).take(indlist)
     90     i.put(indlist, ind)
---> 91     res = func1d(arr[tuple(i.tolist())], *args, **kwargs)
     92     #  if res is a number, then we have a smaller output array
     93     if isscalar(res):

/venv/lib/python3.4/site-packages/pandas/core/window.py in calc(x)
    471 
    472                 def calc(x):
--> 473                     return func(x, window, min_periods=self.min_periods)
    474 
    475             if values.ndim > 1:

/venv/lib/python3.4/site-packages/pandas/core/window.py in func(arg, window, min_periods)
    458                 def func(arg, window, min_periods=None):
    459                     minp = check_minp(min_periods, window)
--> 460                     return cfunc(arg, window, minp, **kwargs)
    461 
    462             # calculation function

pandas/algos.pyx in pandas.algos.roll_max (pandas/algos.c:37363)()

ValueError: Buffer dtype mismatch, expected 'float64_t' but got 'float'

[jreback]

I think I forgot the casting (these should really have dtype specific functions, e.g. float32/float64), but that's your other issue.

> /Users/jreback/pandas/pandas/core/window.py(460)func()
    458                 def func(arg, window, min_periods=None):
    459                     minp = check_minp(min_periods, window)
--> 460                     return cfunc(arg, window, minp, **kwargs)
    461 
    462             # calculation function

ipdb> p arg
array([ 0.,  1.,  2.,  3.,  4.], dtype=float32)
ipdb> p cfunc
<built-in function roll_max>
ipdb> p cfunc(com._ensure_float64(arg), window, minp, **kwargs)
array([ nan,  nan,   2.,   3.,   4.])

want to do a PR to fix?