# Edge Detection [ex110.0]¶

Performs edge detection based on two adjacent ALSSMs, which are connected with linear constraints on its state parameters. Edges are detected on LCR (Log-Cost Ratios) peaks.

Out:

---- MODEL ----
CostSegment : label: None
└- ['Alssm : polynomial, A: (2, 2), C: (1, 2), label: alssm_left', 'Alssm : polynomial, A: (2, 2), C: (1, 2), label: alssm_right'],
└- [Segment : a: -21, b: -1, direction: fw, g: 7, delta: 0, label: None , Segment : a: 0, b: 20, direction: bw, g: 7, delta: 0, label: None ]
Joined ALSSM state labels:  {'offset': (0,), 'v1': (1,), 'v2': (2,)}
/Users/wbr8/homedata/projects/lmlib-branches/reto-doc/lmlib/statespace/costfunc.py:133: UserWarning: This steady state calculation can be numerically unstable due to the inversion of a high conditioned matrix
warnings.warn("This steady state calculation can be numerically unstable due to the inversion of a high conditioned matrix")
---- ESTIMATES ----
Indices of slope changes (reference):  [40, 80, 130, 160, 220]
Indices of slope changes (estimates):  [ 41  80 130 160 292]


import numpy as np
import matplotlib.pyplot as plt
from scipy.signal import find_peaks

import lmlib as lm
from lmlib.utils.generator import gen_slopes, gen_wgn

# Signal
K = 300
k = range(K)
ks = [40, 80, 130, 160, 220]
deltas = [0, 5, -8.5, 3, -2]
y = gen_slopes(K, ks, deltas) + gen_wgn(K, sigma=0.2, seed=3141)

# Model
alssm_left = lm.AlssmPoly(poly_degree=1, label='alssm_left')
alssm_right = lm.AlssmPoly(poly_degree=1, label='alssm_right')
segment_left = lm.Segment(a=-21, b=-1, direction=lm.FORWARD, g=7)
segment_right = lm.Segment(a=0, b=20, direction=lm.BACKWARD, g=7)
F = [[1, 0], [0, 1]]
ccost = lm.CompositeCost((alssm_left, alssm_right), (segment_left, segment_right), F)
print('---- MODEL ----')
print(ccost)

H_line = lm.ConstrainMatrix(ccost).constrain_linear(('alssm_left.x', 'alssm_right.x'), (1, 1), labels=('offset', 'slope'))
# lm.ConstrainH(ccost).constain_linear()
H_edge = lm.ConstrainMatrix(ccost)
H_edge = H_edge.constrain_linear(('alssm_left.x0', 'alssm_right.x0'), (1, 1), labels=('offset',))
print("Joined ALSSM state labels: ", H_edge.v_state_labels)

# Filter
separam.filter(y)
x_hat_edge = separam.minimize_x(H_edge)
x_hat_line = separam.minimize_x(H_line)

# Signal Approximation
y_hat = ccost.eval_alssm(x_hat_edge, alssm_selection=[0, 1])

# Square Error and lcr
error_edge = separam.eval_errors(x_hat_edge, range(K))
error_line = separam.eval_errors(x_hat_line, range(K))
lcr = -1 / 2 * np.log(np.divide(error_edge, error_line))

# Find best matches
peaks, _ = find_peaks(lcr, height=0.2, distance=20)
print('---- ESTIMATES ----')
print('Indices of slope changes (reference): ', ks)
print('Indices of slope changes (estimates): ', peaks)

# Trajectories
trajs_edge = lm.map_trajectories(ccost.trajectories(x_hat_edge[peaks], thds=0.01), peaks, K, merge_ks=True, merge_seg=False)
trajs_line = lm.map_trajectories(ccost.trajectories(x_hat_line[peaks], thds=0.01), peaks, K, merge_ks=True)

# Windows
wins = lm.map_window(ccost.window(segment_selection=[1, 1]), peaks, K, merge_ks=True, fill_value=0)

# Plot
_, axs = plt.subplots(4, 1, sharex='all', figsize=(9, 8))

axs[0].plot(k, wins[0], c='tab:green', label='left window')
axs[0].plot(k, wins[1], c='tab:blue', label='right window')
axs[0].set(xlabel='k', ylabel=r'$w$')
axs[0].legend(loc=1)

axs[1].plot(k, y, lw=0.5, c='k', label='observation')
axs[1].plot(k, trajs_edge[0], lw=1.5, c='tab:green', label='left Alssm edge')
axs[1].plot(k, trajs_edge[1], lw=1.5, c='tab:blue', label='right Alssm edge')
axs[1].plot(k, trajs_line[0], ':',  lw=1, c='tab:gray', label='Alssm line')
axs[1].plot(k, trajs_line[1], ':', lw=1, c='tab:gray')
axs[1].scatter(peaks, y_hat[peaks], marker=7, c='r')
axs[1].set(xlabel='k', ylabel=r'$y$')
axs[1].legend(loc=1)

axs[2].plot(k, error_edge, label="SE edge")
axs[2].plot(k, error_line, label="SE line")
axs[2].set(xlabel='k', ylabel=r'$J$')
axs[2].legend(loc=1)

axs[3].plot(k, lcr)
axs[3].scatter(peaks, lcr[peaks], marker=7, c='r')
axs[3].set(xlabel='k', ylabel='LCR')

plt.show()


Total running time of the script: ( 0 minutes 0.427 seconds)

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