'pad 1d array with zeros at end to have length maxlag
function that is a method, no self used
Parameters
arr : array_like, 1d
array that will be padded with zeros
maxlag : int
length of array after padding
atend : boolean
If True (default), then the zeros are added to the end, otherwise
to the front of the array
Returns
arrp : ndarray
zero-padded array
Notes
This is mainly written to extend coefficient arrays for the lag-polynomials.
It returns a copy.'

def padarr(self, arr, maxlag, atend=True):

    if atend:
        return np.r_[(arr, np.zeros((maxlag - len(arr))))]
    else:
        return np.r_[(np.zeros((maxlag - len(arr))), arr)]
