selectdata
selectdata#
- syncopy.selectdata(data, trials=None, channel=None, channel_i=None, channel_j=None, latency=None, frequency=None, taper=None, unit=None, eventid=None, inplace=False, clear=False, parallel=None, **kwargs)[source]#
Create a new Syncopy object from a selection
Usage Notice
Syncopy offers two modes for selecting data:
in-place selections mark subsets of a Syncopy data object for processing via a
select
dictionary without creating a new objectdeep-copy selections copy subsets of a Syncopy data object to keep and preserve in a new object created by
selectdata()
All Syncopy metafunctions, such as
freqanalysis()
, support in-place data selection via aselect
keyword, effectively avoiding potentially slow copy operations and saving disk space. The keys accepted by the select dictionary are identical to the keyword arguments discussed below. In addition,select = "all"
can be used to select entire object contents. Examples>>> select = {"toilim" : [-0.25, 0]} >>> spy.freqanalysis(data, select=select) >>> # or equivalently >>> cfg = spy.get_defaults(spy.freqanalysis) >>> cfg.select = select >>> spy.freqanalysis(cfg, data)
Usage Summary
List of Syncopy data objects and respective valid data selectors:
AnalogData
trials, channel, toi/toilimExamples
>>> spy.selectdata(data, trials=[0, 3, 5], channel=["channel01", "channel02"]) >>> cfg = spy.StructDict() >>> cfg.trials = [5, 3, 0]; cfg.toilim = [0.25, 0.5] >>> spy.selectdata(cfg, data)
SpectralData
trials, channel, toi/toilim, foi/foilim, taperExamples
>>> spy.selectdata(data, trials=[0, 3, 5], channel=["channel01", "channel02"]) >>> cfg = spy.StructDict() >>> cfg.foi = [30, 40, 50]; cfg.taper = slice(2, 4) >>> spy.selectdata(cfg, data)
EventData
trials, toi/toilim, eventidExamples
>>> spy.selectdata(data, toilim=[-1, 2.5], eventid=[0, 1]) >>> cfg = spy.StructDict() >>> cfg.trials = [0, 0, 1, 0]; cfg.eventid = slice(2, None) >>> spy.selectdata(cfg, data)
SpikeData
trials, toi/toilim, unit, channelExamples
>>> spy.selectdata(data, toilim=[-1, 2.5], unit=range(0, 10)) >>> cfg = spy.StructDict() >>> cfg.toi = [1.25, 3.2]; cfg.trials = [0, 1, 2, 3] >>> spy.selectdata(cfg, data)
Note Any property that is not specifically accessed via one of the provided selectors is taken as is, e.g.,
spy.selectdata(data, trials=[1, 2])
selects the entire contents of trials no. 2 and 3, whilespy.selectdata(data, channel=range(0, 50))
selects the first 50 channels of data across all defined trials. Consequently, if no keywords are specified, the entire contents of data is selected.Full documentation below
The parameters listed below can be provided as is or a via a cfg configuration ‘structure’, see Notes for details.
- Parameters
data (Syncopy data object) – A non-empty Syncopy data object. Note the type of data determines which keywords can be used. Some keywords are only valid for certain types of Syncopy objects, e.g., “freqs” is not a valid selector for an
AnalogData
object.trials (list (integers) or None or "all") – List of integers representing trial numbers to be selected; can include repetitions and need not be sorted (e.g.,
trials = [0, 1, 0, 0, 2]
is valid) but must be finite and not NaN. If trials is None, ortrials = "all"
all trials are selected.channel (list (integers or strings), slice, range, str, int, None or "all") – Channel-selection; can be a list of channel names (
['channel3', 'channel1']
), a list of channel indices ([3, 5]
), a slice (slice(3, 10)
) or range (range(3, 10)
). Note that following Python conventions, channels are counted starting at zero, and range and slice selections are half-open intervals of the form [low, high), i.e., low is included , high is excluded. Thus,channel = [0, 1, 2]
orchannel = slice(0, 3)
selects the first up to (and including) the third channel. Selections can be unsorted and may include repetitions but must match exactly, be finite and not NaN. If channel is None, orchannel = "all"
all channels are selected.latency ([begin, end], {'maxperiod', 'minperiod', 'prestim', 'poststim', 'all'} or None) – Either set desired time window ([begin, end]) in seconds, ‘maxperiod’ (default) for the maximum period available or ‘minperiod’ for minimal time-window all trials share, or `’prestim’ (all t < 0) or ‘poststim’ (all t > 0) If set this will apply a selection which is timelocked, meaning non-fitting (effectively too short) trials will be excluded
frequency (list (floats [fmin, fmax]) or None or "all") – Frequency-window
[fmin, fmax]
(in Hz) to be extracted. Window specifications must be sorted (e.g.,[90, 70]
is invalid) and not NaN but may be unbounded (e.g.,[-np.inf, 60.5]
is valid). Edges fmin and fmax are included in the selection. If foilim is None orfoilim = "all"
, all frequencies are selected.taper (list (integers or strings), slice, range, str, int, None or "all") – Taper-selection; can be a list of taper names (
['dpss-win-1', 'dpss-win-3']
), a list of taper indices ([3, 5]
), a slice (slice(3, 10)
) or range (range(3, 10)
). Note that following Python conventions, tapers are counted starting at zero, and range and slice selections are half-open intervals of the form [low, high), i.e., low is included , high is excluded. Thus,taper = [0, 1, 2]
ortaper = slice(0, 3)
selects the first up to (and including) the third taper. Selections can be unsorted and may include repetitions but must match exactly, be finite and not NaN. If taper is None ortaper = "all"
, all tapers are selected.unit (list (integers or strings), slice, range, str, int, None or "all") – Unit-selection; can be a list of unit names (
['unit10', 'unit3']
), a list of unit indices ([3, 5]
), a slice (slice(3, 10)
) or range (range(3, 10)
). Note that following Python conventions, units are counted starting at zero, and range and slice selections are half-open intervals of the form [low, high), i.e., low is included , high is excluded. Thus,unit = [0, 1, 2]
orunit = slice(0, 3)
selects the first up to (and including) the third unit. Selections can be unsorted and may include repetitions but must match exactly, be finite and not NaN. If unit is None orunit = "all"
, all units are selected.eventid (list (integers), slice, range, int, None or "all") – Event-ID-selection; can be a list of event-id codes (
[2, 0, 1]
), slice (slice(0, 2)
) or range (range(0, 2)
). Note that following Python conventions, range and slice selections are half-open intervals of the form [low, high), i.e., low is included , high is excluded. Selections can be unsorted and may include repetitions but must match exactly, be finite and not NaN. If eventid is None oreventid = "all"
, all events are selected.inplace (bool) – If inplace is True no new object is created. Instead the provided selection is stored in the input object’s selection attribute for later use. By default inplace is False and all calls to selectdata create a new Syncopy data object.
clear (bool) – If True remove any active in-place selection. Note that in-place selections can also be removed manually by assinging None to the selection property, i.e.,
mydata.selection = None
is equivalent tospy.selectdata(mydata, clear=True)
ormydata.selectdata(clear=True)
parallel (None or bool) – If None (recommended), processing is automatically performed in parallel (i.e., concurrently across trials/channel-groups), provided a dask parallel processing client is running and available. Parallel processing can be manually disabled by setting parallel to False. If parallel is True but no parallel processing client is running, computing will be performed sequentially.
- Returns
dataselection – Syncopy data object of the same type as data but containing only the subset specified by provided selectors.
- Return type
Syncopy data object
Notes
This function can be either called providing its input arguments directly or via a cfg configuration ‘structure’. For instance, the following function calls are equivalent
>>> spy.selectdata(data, trials=...) >>> cfg = spy.StructDict() >>> cfg.trials = ... >>> spy.selectdata(cfg, data) >>> cfg.data = data >>> spy.selectdata(cfg)
Please refer to Syncopy for FieldTrip Users for further details.
This routine represents a convenience function for creating new Syncopy objects based on existing data entities. However, in many situations, the creation of a new object (and thus the allocation of additional disk-space) might not be necessary: all Syncopy metafunctions, such as
freqanalysis()
, support in-place data selection.Consider the following example: assume data is an
AnalogData
object representing 220 trials of LFP recordings containing baseline (between second -0.25 and 0) and stimulus-on data (on the interval [0.25, 0.5]). To compute the baseline spectrum, data-selection does not have to be performed before callingfreqanalysis()
but instead can be done in-place:>>> import syncopy as spy >>> cfg = spy.get_defaults(spy.freqanalysis) >>> cfg.method = 'mtmfft' >>> cfg.taper = 'dpss' >>> cfg.output = 'pow' >>> cfg.tapsmofrq = 10 >>> # define baseline/stimulus-on ranges >>> baseSelect = {"toilim": [-0.25, 0]} >>> stimSelect = {"toilim": [0.25, 0.5]} >>> # in-place selection of baseline interval performed by `freqanalysis` >>> cfg.select = baseSelect >>> baselineSpectrum = spy.freqanalysis(cfg, data) >>> # in-place selection of stimulus-on time-frame performed by `freqanalysis` >>> cfg.select = stimSelect >>> stimonSpectrum = spy.freqanalysis(cfg, data)
Especially for large data-sets, in-place data selection performed by Syncopy’s metafunctions does not only save disk-space but can significantly increase performance.
Examples
Use
generate_artificial_data()
to create a syntheticsyncopy.AnalogData
object.>>> from syncopy.tests.misc import generate_artificial_data >>> adata = generate_artificial_data(nTrials=10, nChannels=32)
Assume a hypothetical trial onset at second 2.0 with the first second of each trial representing baseline recordings. To extract only the stimulus-on period from adata, one could use
>>> stimon = spy.selectdata(adata, toilim=[2.0, np.inf])
Note that this is equivalent to
>>> stimon = adata.selectdata(toilim=[2.0, np.inf])
See also
syncopy.show()
Show (subsets) of Syncopy objects