mne.time_frequency.CrossSpectralDensity¶

class
mne.time_frequency.
CrossSpectralDensity
(data, ch_names, frequencies, n_fft, tmin=None, tmax=None, projs=None)[source]¶ Crossspectral density.
Given a list of time series, the CSD matrix denotes for each pair of time series, the crossspectral density. This matrix is symmetric and internally stored as a vector.
This object can store multiple CSD matrices: one for each frequency. Use
.get_data(freq)
to obtain an CSD matrix as an ndarray. Parameters
 data
ndarray
, shape ((n_channels**2 + n_channels) // 2, n_frequencies) For each frequency, the crossspectral density matrix in vector format.
 ch_names
list
ofstr
List of string names for each channel.
 frequencies
float
list
offloat
list
oflist
offloat
Frequency or frequencies for which the CSD matrix was calculated. When averaging across frequencies (see the
CrossSpectralDensity.mean()
function), this will be a list of lists that contains for each frequency bin, the frequencies that were averaged. Frequencies should always be sorted. n_fft
int
The number of FFT points or samples that have been used in the computation of this CSD.
 tmin
float
None
Start of the time window for which CSD was calculated in seconds. Can be
None
(the default) to indicate no timing information is available. tmax
float
None
End of the time window for which CSD was calculated in seconds. Can be
None
(the default) to indicate no timing information is available. projs
list
ofProjection
None
List of projectors to apply to timeseries data when using this CSD object to compute a DICS beamformer. Defaults to
None
, which means no projectors will be applied.
 data
See also
 Attributes
n_channels
Number of time series defined in this CSD object.
Methods
__getitem__
(sel)Subselect frequencies.
__hash__
(/)Return hash(self).
__len__
()Return number of frequencies.
copy
()Return copy of the CrossSpectralDensity object.
get_data
([frequency, index, as_cov])Get the CSD matrix for a given frequency as NumPy array.
mean
([fmin, fmax])Calculate the mean CSD in the given frequency range(s).
pick_channels
(ch_names[, ordered])Pick channels from this crossspectral density matrix.
pick_frequency
([freq, index])Get a CrossSpectralDensity object with only the given frequency.
plot
([info, mode, colorbar, cmap, n_cols, show])Plot CSD matrices.
save
(fname)Save the CSD to an HDF5 file.
sum
([fmin, fmax])Calculate the sum CSD in the given frequency range(s).

__getitem__
(sel)[source]¶ Subselect frequencies.
 Parameters
 sel
ndarray
Array of frequency indices to subselect.
 sel
 Returns
 csdinstance of
CrossSpectralDensity
A new CSD instance with the subset of frequencies.
 csdinstance of

copy
()[source]¶ Return copy of the CrossSpectralDensity object.
 Returns
 copyinstance of
CrossSpectralDensity
A copy of the object.
 copyinstance of

get_data
(frequency=None, index=None, as_cov=False)[source]¶ Get the CSD matrix for a given frequency as NumPy array.
If there is only one matrix defined in the CSD object, calling this method without any parameters will return it. If multiple matrices are defined, use either the
frequency
orindex
parameter to select one. Parameters
 frequency
float
None
Return the CSD matrix for a specific frequency. Only available when no averaging across frequencies has been done.
 index
int
None
Return the CSD matrix for the frequency or frequencybin with the given index.
 as_covbool
Whether to return the data as a numpy array (
False
, the default), or pack it in amne.Covariance
object (True
).New in version 0.20.
 frequency
 Returns
 csd
ndarray
, shape (n_channels, n_channels)  instance ofCovariance
The CSD matrix corresponding to the requested frequency.
 csd
See also

mean
(fmin=None, fmax=None)[source]¶ Calculate the mean CSD in the given frequency range(s).
 Parameters
 fmin
float
list
offloat
None
Lower bound of the frequency range in Hertz. Defaults to the lowest frequency available. When a list of frequencies is given, these are used as the lower bounds (inclusive) of frequency bins and the mean is taken for each bin.
 fmax
float
list
offloat
None
Upper bound of the frequency range in Hertz. Defaults to the highest frequency available. When a list of frequencies is given, these are used as the upper bounds (inclusive) of frequency bins and the mean is taken for each bin.
 fmin
 Returns
 csdinstance of
CrossSpectralDensity
The CSD matrix, averaged across the given frequency range(s).
 csdinstance of
Examples using
mean
:

property
n_channels
¶ Number of time series defined in this CSD object.

pick_channels
(ch_names, ordered=False)[source]¶ Pick channels from this crossspectral density matrix.
 Parameters
 Returns
 csdinstance of CrossSpectralDensity.
The modified crossspectral density object.
Notes
Operates inplace.
New in version 0.20.0.

pick_frequency
(freq=None, index=None)[source]¶ Get a CrossSpectralDensity object with only the given frequency.
 Parameters
 Returns
 csdinstance of
CrossSpectralDensity
A CSD object containing a single CSD matrix that corresponds to the requested frequency or frequencybin.
 csdinstance of
See also

plot
(info=None, mode='csd', colorbar=True, cmap='viridis', n_cols=None, show=True)[source]¶ Plot CSD matrices.
A subplot is created for each frequency. If an info object is passed to the function, different channel types are plotted in different figures.
 Parameters
 infoinstance of
Info
None
To split the figure by channeltype, provide the measurement info. By default, the CSD matrix is plotted as a whole.
 mode‘csd’  ‘coh’
Whether to plot the crossspectral density (‘csd’, the default), or the coherence (‘coh’) between the channels.
 colorbarbool
Whether to show a colorbar. Defaults to
True
. cmap
str
None
The matplotlib colormap to use. Defaults to None, which means the colormap will default to matplotlib’s default.
 n_cols
int
None
CSD matrices are plotted in a grid. This parameter controls how many matrix to plot side by side before starting a new row. By default, a number will be chosen to make the grid as square as possible.
 showbool
Whether to show the figure. Defaults to
True
.
 infoinstance of
 Returns

save
(fname)[source]¶ Save the CSD to an HDF5 file.
 Parameters
 fname
str
The name of the file to save the CSD to. The extension ‘.h5’ will be appended if the given filename doesn’t have it already.
 fname
See also
read_csd
For reading CSD objects from a file.

sum
(fmin=None, fmax=None)[source]¶ Calculate the sum CSD in the given frequency range(s).
If the exact given frequencies are not available, the nearest frequencies will be chosen.
 Parameters
 fmin
float
list
offloat
None
Lower bound of the frequency range in Hertz. Defaults to the lowest frequency available. When a list of frequencies is given, these are used as the lower bounds (inclusive) of frequency bins and the sum is taken for each bin.
 fmax
float
list
offloat
None
Upper bound of the frequency range in Hertz. Defaults to the highest frequency available. When a list of frequencies is given, these are used as the upper bounds (inclusive) of frequency bins and the sum is taken for each bin.
 fmin
 Returns
 csdinstance of
CrossSpectralDensity
The CSD matrix, summed across the given frequency range(s).
 csdinstance of
Examples using
sum
: