scipy.signal.find_peaks_cwt¶

scipy.signal.
find_peaks_cwt
(vector, widths, wavelet=None, max_distances=None, gap_thresh=None, min_length=None, min_snr=1, noise_perc=10)[source]¶ Find peaks in a 1D array with wavelet transformation.
The general approach is to smooth vector by convolving it with wavelet(width) for each width in widths. Relative maxima which appear at enough length scales, and with sufficiently high SNR, are accepted.
Parameters:  vector : ndarray
1D array in which to find the peaks.
 widths : sequence
1D array of widths to use for calculating the CWT matrix. In general, this range should cover the expected width of peaks of interest.
 wavelet : callable, optional
Should take two parameters and return a 1D array to convolve with vector. The first parameter determines the number of points of the returned wavelet array, the second parameter is the scale (width) of the wavelet. Should be normalized and symmetric. Default is the ricker wavelet.
 max_distances : ndarray, optional
At each row, a ridge line is only connected if the relative max at row[n] is within
max_distances[n]
from the relative max atrow[n+1]
. Default value iswidths/4
. gap_thresh : float, optional
If a relative maximum is not found within max_distances, there will be a gap. A ridge line is discontinued if there are more than gap_thresh points without connecting a new relative maximum. Default is the first value of the widths array i.e. widths[0].
 min_length : int, optional
Minimum length a ridge line needs to be acceptable. Default is
cwt.shape[0] / 4
, ie 1/4th the number of widths. min_snr : float, optional
Minimum SNR ratio. Default 1. The signal is the value of the cwt matrix at the shortest length scale (
cwt[0, loc]
), the noise is the noise_perc`th percentile of datapoints contained within a window of `window_size aroundcwt[0, loc]
. noise_perc : float, optional
When calculating the noise floor, percentile of data points examined below which to consider noise. Calculated using stats.scoreatpercentile. Default is 10.
Returns:  peaks_indices : ndarray
Indices of the locations in the vector where peaks were found. The list is sorted.
See also
cwt
 Continuous wavelet transform.
find_peaks
 Find peaks inside a signal based on peak properties.
Notes
This approach was designed for finding sharp peaks among noisy data, however with proper parameter selection it should function well for different peak shapes.
 The algorithm is as follows:
 Perform a continuous wavelet transform on vector, for the supplied
widths. This is a convolution of vector with wavelet(width) for
each width in widths. See
cwt
 Identify “ridge lines” in the cwt matrix. These are relative maxima at each row, connected across adjacent rows. See identify_ridge_lines
 Filter the ridge_lines using filter_ridge_lines.
 Perform a continuous wavelet transform on vector, for the supplied
widths. This is a convolution of vector with wavelet(width) for
each width in widths. See
New in version 0.11.0.
References
[1] Bioinformatics (2006) 22 (17): 20592065. DOI:10.1093/bioinformatics/btl355 http://bioinformatics.oxfordjournals.org/content/22/17/2059.long Examples
>>> from scipy import signal >>> xs = np.arange(0, np.pi, 0.05) >>> data = np.sin(xs) >>> peakind = signal.find_peaks_cwt(data, np.arange(1,10)) >>> peakind, xs[peakind], data[peakind] ([32], array([ 1.6]), array([ 0.9995736]))