'Decimate the evoked data.
.. note:: No filtering is performed. To avoid aliasing, ensure
your data are properly lowpassed.
Parameters
decim : int
The amount to decimate data.
offset : int
Apply an offset to where the decimation starts relative to the
sample corresponding to t=0. The offset is in samples at the
current sampling rate.
Returns
evoked : instance of Evoked
The decimated Evoked object.
See Also
Epochs.decimate
Epochs.resample
mne.io.Raw.resample
Notes
Decimation can be done multiple times. For example,
``evoked.decimate(2).decimate(2)`` will be the same as
``evoked.decimate(4)``.
.. versionadded:: 0.13.0'

def decimate(self, decim, offset=0):

    (decim, offset, new_sfreq) = _check_decim(self.info, decim, offset)
    start_idx = int(round((self.times[0] * (self.info['sfreq'] * decim))))
    i_start = ((start_idx % decim) + offset)
    decim_slice = slice(i_start, None, decim)
    self.info['sfreq'] = new_sfreq
    self.data = self.data[:, decim_slice].copy()
    self.times = self.times[decim_slice].copy()
    return self
