yasa.simulate_hypnogram

yasa.simulate_hypnogram(tib=480, trans_probas=None, init_probas=None, seed=None, **kwargs)

Simulate a hypnogram based on transition probabilities.

Current implentation is a naive Markov model. The initial stage of a hypnogram is generated using probabilites from init_probas and then subsequent stages are generated from a Markov sequence based on trans_probas.

Important

The Markov simulation model is not meant to accurately portray sleep macroarchitecture and should only be used for testing or other unique purposes.

See also

yasa.Hypnogram.simulate_similar

Added in version 0.6.3.

Parameters:

tibint, float

Total duration of the hypnogram (i.e., time in bed), expressed in minutes. Returned hypnogram will be slightly shorter if tib is not evenly divisible by freq. Default is 480 minutes (= 8 hours).

See also

yasa.sleep_statistics

trans_probaspandas.DataFrame or None

Transition probability matrix where each cell is a transition probability between sleep stages of consecutive epochs.

trans_probas is a right stochastic matrix, i.e. each row sums to 1.

If None (default), transition probabilities come from Metzner et al., 2021 [Metzner2021]. If pandas.DataFrame, must have “from”-stages as indices and “to”-stages as columns. Indices and columns must follow YASA string hypnogram convention (e.g., WAKE, N1). Unscored/Artefact stages are not allowed.

Note

Transition probability matrices should indicate the transition probability between epochs (i.e., probability of the next epoch) and not simply stage (i.e., probability of non-similar stage).

See also

Return value from yasa.transition_matrix

init_probaspandas.Series or None

Probabilites of each stage to initialize random walk. If None (default), initialize with “from”-WAKE row of trans_probas. If pandas.Series, indices must be stages following YASA string hypnogram convention and identical to those of trans_probas.

seedint or None

Random seed for generating Markov sequence. If an integer number is provided, the random hypnogram will be predictable. This argument is required if reproducible results are desired.

**kwargsdict

Other arguments that are passed to yasa.Hypnogram.

Note

n_stages and freq must be consistent with a user-specificied trans_probas.

Returns:

hypyasa.Hypnogram

Hypnogram containing simulated sleep stages.

Notes

Default transition probabilities are based on 30-second epochs and can be found in the traMat_Epoch.npy file of Supplementary Information for Metzner et al., 2021 [Metzner2021] (rounded values are viewable in Figure 5b). Please cite this work if these probabilites are used for publication.

References

[Metzner2021] (1,2)

Metzner, C., Schilling, A., Traxdorf, M., Schulze, H., & Krausse, P. (2021). Sleep as a random walk: a super-statistical analysis of EEG data across sleep stages. Communications Biology, 4. https://doi.org/10.1038/s42003-021-02912-6

Examples

>>> from yasa import simulate_hypnogram
>>> hyp = simulate_hypnogram(tib=5, seed=1)
>>> hyp
<Hypnogram | 10 epochs x 30s (5.00 minutes), 5 unique stages>
 - Use `.hypno` to get the string values as a pandas.Series
 - Use `.as_int()` to get the integer values as a pandas.Series
 - Use `.plot_hypnogram()` to plot the hypnogram
See the online documentation for more details.

>>> hyp.hypno
Epoch
0    WAKE
1      N1
2      N1
3      N2
4      N2
5      N2
6      N2
7      N2
8      N2
9      N2
Name: Stage, dtype: object

>>> hyp = simulate_hypnogram(tib=5, n_stages=2, seed=1)
>>> hyp.hypno
Epoch
0     WAKE
1    SLEEP
2    SLEEP
3    SLEEP
4    SLEEP
5    SLEEP
6    SLEEP
7    SLEEP
8    SLEEP
9    SLEEP
Name: Stage, dtype: object

Add some Unscored epochs.

>>> hyp = simulate_hypnogram(tib=5, n_stages=2, seed=1)
>>> hyp.hypno.iloc[-2:] = "UNS"
>>> hyp.hypno
Epoch
0     WAKE
1    SLEEP
2    SLEEP
3    SLEEP
4    SLEEP
5    SLEEP
6    SLEEP
7    SLEEP
8      UNS
9      UNS
Name: Stage, dtype: object

Base the data off a real subject’s transition matrix.

>>> import numpy as np
>>> import matplotlib.pyplot as plt
>>> from yasa import Hypnogram, hypno_int_to_str
>>> url = (
>>>     "https://github.com/raphaelvallat/yasa/raw/master/"
>>>     "notebooks/data_full_6hrs_100Hz_hypno_30s.txt"
>>> )
>>> values_str = hypno_int_to_str(np.loadtxt(url))
>>> real_hyp = Hypnogram(values_str)
>>> fake_hyp = real_hyp.simulate_similar(seed=2)
>>> fig, (ax1, ax2) = plt.subplots(nrows=2, figsize=(7, 5))
>>> real_hyp.plot_hypnogram(ax=ax1).set_title("Real hypnogram")
>>> fake_hyp.plot_hypnogram(ax=ax2).set_title("Fake hypnogram")
>>> plt.tight_layout()