1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
.. contents:: Contents
:local:
:depth: 3
.. _memory:
Memory-efficient IO
###################
Preloading
==========
Raw
^^^
MNE-Python can read data on-demand using the ``preload`` option provided in :ref:`IO functions <ch_convert>`. For example::
from mne import io
from mne.datasets import sample
data_path = sample.data_path()
raw_fname = data_path + '/MEG/sample/sample_audvis_filt-0-40_raw.fif'
raw = io.read_raw_fif(raw_fname, preload=False)
.. note:: Filtering does not work with ``preload=False``.
Epochs
^^^^^^
Similarly, epochs can also be be read from disk on-demand. For example::
import mne
events = mne.find_events(raw)
event_id, tmin, tmax = 1, -0.2, 0.5
picks = mne.pick_types(raw.info, meg=True, eeg=True, stim=False, eog=True)
epochs = mne.Epochs(raw, events, event_id, tmin, tmax, picks=picks, baseline=(None, 0), reject=dict(eeg=80e-6, eog=150e-6),
preload=False)
When ``preload=False``, the epochs data is loaded from the disk on-demand. Note that ``preload=False`` for epochs will work even if the ``raw`` object
has been loaded with ``preload=True``. Preloading is also supported for :func:`mne.read_epochs`.
.. warning:: This comes with a caveat. When ``preload=False``, data rejection based on peak-to-peak thresholds is executed when the data is loaded from disk, *not* when the ``Epochs`` object is created.
To explicitly reject artifacts with ``preload=False``, use the function :func:`mne.Epochs.drop_bad`.
Loading data explicitly
=======================
To load the data if ``preload=False`` was initially selected, use the functions :func:`mne.io.Raw.load_data` and :func:`mne.Epochs.load_data`.
|
