librosa.segment.lag_to_recurrence

librosa.segment.lag_to_recurrence(lag, *, axis=-1)[source]

Convert a lag matrix into a recurrence matrix.

Parameters
lagnp.ndarray or scipy.sparse.spmatrix

A lag matrix, as produced by recurrence_to_lag

axisint

The axis corresponding to the time dimension. The alternate axis will be interpreted in lag coordinates.

Returns
recnp.ndarray or scipy.sparse.spmatrix [shape=(n, n)]

A recurrence matrix in (time, time) coordinates For sparse matrices, format will match that of lag.

Raises
ParameterErrorif lag does not have the correct shape

Examples

>>> y, sr = librosa.load(librosa.ex('nutcracker'))
>>> hop_length = 1024
>>> chroma = librosa.feature.chroma_cqt(y=y, sr=sr, hop_length=hop_length)
>>> chroma_stack = librosa.feature.stack_memory(chroma, n_steps=10, delay=3)
>>> recurrence = librosa.segment.recurrence_matrix(chroma_stack)
>>> lag_pad = librosa.segment.recurrence_to_lag(recurrence, pad=True)
>>> lag_nopad = librosa.segment.recurrence_to_lag(recurrence, pad=False)
>>> rec_pad = librosa.segment.lag_to_recurrence(lag_pad)
>>> rec_nopad = librosa.segment.lag_to_recurrence(lag_nopad)
>>> import matplotlib.pyplot as plt
>>> fig, ax = plt.subplots(nrows=2, ncols=2, sharex=True)
>>> librosa.display.specshow(lag_pad, x_axis='s', y_axis='lag',
...                          hop_length=hop_length, ax=ax[0, 0])
>>> ax[0, 0].set(title='Lag (zero-padded)')
>>> ax[0, 0].label_outer()
>>> librosa.display.specshow(lag_nopad, x_axis='s', y_axis='time',
...                          hop_length=hop_length, ax=ax[0, 1])
>>> ax[0, 1].set(title='Lag (no padding)')
>>> ax[0, 1].label_outer()
>>> librosa.display.specshow(rec_pad, x_axis='s', y_axis='time',
...                          hop_length=hop_length, ax=ax[1, 0])
>>> ax[1, 0].set(title='Recurrence (with padding)')
>>> librosa.display.specshow(rec_nopad, x_axis='s', y_axis='time',
...                          hop_length=hop_length, ax=ax[1, 1])
>>> ax[1, 1].set(title='Recurrence (without padding)')
>>> ax[1, 1].label_outer()
../_images/librosa-segment-lag_to_recurrence-1.png