def gamboa_segmenter(signal=None, sampling_rate=1000., tol=0.002):
"""ECG R-peak segmentation algorithm.
Follows the approach by Gamboa.
Parameters
----------
signal : array
Input filtered ECG signal.
sampling_rate : int, float, optional
Sampling frequency (Hz).
tol : float, optional
Tolerance parameter.
Returns
-------
rpeaks : array
R-peak location indices.
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
# convert to samples
v_100ms = int(0.1 * sampling_rate)
v_300ms = int(0.3 * sampling_rate)
hist, edges = np.histogram(signal, 100, density=True)
TH = 0.01
F = np.cumsum(hist)
v0 = edges[np.nonzero(F > TH)[0][0]]
v1 = edges[np.nonzero(F < (1 - TH))[0][-1]]
nrm = max([abs(v0), abs(v1)])
norm_signal = signal / float(nrm)
d2 = np.diff(norm_signal, 2)
b = np.nonzero((np.diff(np.sign(np.diff(-d2)))) == -2)[0] + 2
b = np.intersect1d(b, np.nonzero(-d2 > tol)[0])
if len(b) < 3:
rpeaks = []
else:
b = b.astype('float')
rpeaks = []
previous = b[0]
for i in b[1:]:
if i - previous > v_300ms:
previous = i
rpeaks.append(np.argmax(signal[int(i):int(i + v_100ms)]) + i)
rpeaks = sorted(list(set(rpeaks)))
rpeaks = np.array(rpeaks, dtype='int')
return utils.ReturnTuple((rpeaks, ), ('rpeaks', ))
def extract_heartbeats(signal=None,
rpeaks=None,
sampling_rate=1000.,
before=0.2,
after=0.4):
"""Extract heartbeat templates from an ECG signal, given a list of
R-peak locations.
Parameters
----------
signal : array
Input ECG signal.
rpeaks : array
R-peak location indices.
sampling_rate : int, float, optional
Sampling frequency (Hz).
before : float, optional
Window size to include before the R peak (seconds).
after : int, optional
Window size to include after the R peak (seconds).
Returns
-------
templates : array
Extracted heartbeat templates.
rpeaks : array
Corresponding R-peak location indices of the extracted heartbeat
templates.
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
if rpeaks is None:
raise TypeError("Please specify the input R-peak locations.")
if before < 0:
raise ValueError("Please specify a non-negative 'before' value.")
if after < 0:
raise ValueError("Please specify a non-negative 'after' value.")
# convert delimiters to samples
before = int(before * sampling_rate)
after = int(after * sampling_rate)
# get heartbeats
templates, newR = _extract_heartbeats(signal=signal,
rpeaks=rpeaks,
before=before,
after=after)
return utils.ReturnTuple((templates, newR), ('templates', 'rpeaks'))
def correct_rpeaks(signal=None, rpeaks=None, sampling_rate=1000., tol=0.05):
"""Correct R-peak locations to the maximum within a tolerance.
Parameters
----------
signal : array
ECG signal.
rpeaks : array
R-peak location indices.
sampling_rate : int, float, optional
Sampling frequency (Hz).
tol : int, float, optional
Correction tolerance (seconds).
Returns
-------
rpeaks : array
Cerrected R-peak location indices.
Notes
-----
* The tolerance is defined as the time interval :math:`[R-tol, R+tol[`.
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
if rpeaks is None:
raise TypeError("Please specify the input R-peaks.")
tol = int(tol * sampling_rate)
length = len(signal)
newR = []
for r in rpeaks:
a = r - tol
if a < 0:
continue
b = r + tol
if b > length:
break
newR.append(a + np.argmax(signal[a:b]))
newR = sorted(list(set(newR)))
newR = np.array(newR, dtype='int')
return utils.ReturnTuple((newR, ), ('rpeaks', ))
def hamilton_segmenter(signal=None, sampling_rate=1000.):
"""ECG R-peak segmentation algorithm.
Follows the approach by Hamilton [Hami02]_.
Parameters
----------
signal : array
Input filtered ECG signal.
sampling_rate : int, float, optional
Sampling frequency (Hz).
Returns
-------
rpeaks : array
R-peak location indices.
References
----------
.. [Hami02] P.S. Hamilton, "Open Source ECG Analysis Software
Documentation", E.P.Limited, 2002
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
sampling_rate = float(sampling_rate)
length = len(signal)
dur = length / sampling_rate
# algorithm parameters
v1s = int(1. * sampling_rate)
v100ms = int(0.1 * sampling_rate)
TH_elapsed = np.ceil(0.36 * sampling_rate)
sm_size = int(0.08 * sampling_rate)
init_ecg = 8 # seconds for initialization
if dur < init_ecg:
init_ecg = int(dur)
# filtering
filtered, _, _ = st.filter_signal(signal=signal,
ftype='butter',
band='lowpass',
order=4,
frequency=25.,
sampling_rate=sampling_rate)
filtered, _, _ = st.filter_signal(signal=filtered,
ftype='butter',
band='highpass',
order=4,
frequency=3.,
sampling_rate=sampling_rate)
# diff
dx = np.abs(np.diff(filtered, 1) * sampling_rate)
# smoothing
dx, _ = st.smoother(signal=dx, kernel='hamming', size=sm_size, mirror=True)
# buffers
qrspeakbuffer = np.zeros(init_ecg)
noisepeakbuffer = np.zeros(init_ecg)
peak_idx_test = np.zeros(init_ecg)
noise_idx = np.zeros(init_ecg)
rrinterval = sampling_rate * np.ones(init_ecg)
a, b = 0, v1s
all_peaks, _ = st.find_extrema(signal=dx, mode='max')
for i in range(init_ecg):
peaks, values = st.find_extrema(signal=dx[a:b], mode='max')
try:
ind = np.argmax(values)
except ValueError:
pass
else:
# peak amplitude
qrspeakbuffer[i] = values[ind]
# peak location
peak_idx_test[i] = peaks[ind] + a
a += v1s
b += v1s
# thresholds
ANP = np.median(noisepeakbuffer)
AQRSP = np.median(qrspeakbuffer)
TH = 0.475
DT = ANP + TH * (AQRSP - ANP)
DT_vec = []
indexqrs = 0
indexnoise = 0
indexrr = 0
npeaks = 0
offset = 0
beats = []
# detection rules
# 1 - ignore all peaks that precede or follow larger peaks by less than 200ms
lim = int(np.ceil(0.2 * sampling_rate))
diff_nr = int(np.ceil(0.045 * sampling_rate))
bpsi, bpe = offset, 0
for f in all_peaks:
DT_vec += [DT]
# 1 - Checking if f-peak is larger than any peak following or preceding it by less than 200 ms
peak_cond = np.array(
(all_peaks > f - lim) * (all_peaks < f + lim) * (all_peaks != f))
peaks_within = all_peaks[peak_cond]
if peaks_within.any() and (max(dx[peaks_within]) > dx[f]):
continue
# 4 - If the peak is larger than the detection threshold call it a QRS complex, otherwise call it noise
if dx[f] > DT:
# 2 - look for both positive and negative slopes in raw signal
if f < diff_nr:
diff_now = np.diff(signal[0:f + diff_nr])
elif f + diff_nr >= len(signal):
diff_now = np.diff(signal[f - diff_nr:len(dx)])
else:
diff_now = np.diff(signal[f - diff_nr:f + diff_nr])
diff_signer = diff_now[diff_now > 0]
if len(diff_signer) == 0 or len(diff_signer) == len(diff_now):
continue
# RR INTERVALS
if npeaks > 0:
# 3 - in here we check point 3 of the Hamilton paper
# that is, we check whether our current peak is a valid R-peak.
prev_rpeak = beats[npeaks - 1]
elapsed = f - prev_rpeak
# if the previous peak was within 360 ms interval
if elapsed < TH_elapsed:
# check current and previous slopes
if prev_rpeak < diff_nr:
diff_prev = np.diff(signal[0:prev_rpeak + diff_nr])
elif prev_rpeak + diff_nr >= len(signal):
diff_prev = np.diff(signal[prev_rpeak -
diff_nr:len(dx)])
else:
diff_prev = np.diff(
signal[prev_rpeak - diff_nr:prev_rpeak + diff_nr])
slope_now = max(diff_now)
slope_prev = max(diff_prev)
if (slope_now < 0.5 * slope_prev):
# if current slope is smaller than half the previous one, then it is a T-wave
continue
if dx[f] < 3. * np.median(
qrspeakbuffer): # avoid retarded noise peaks
beats += [int(f) + bpsi]
else:
continue
if bpe == 0:
rrinterval[indexrr] = beats[npeaks] - beats[npeaks - 1]
indexrr += 1
if indexrr == init_ecg:
indexrr = 0
else:
if beats[npeaks] > beats[bpe - 1] + v100ms:
rrinterval[indexrr] = beats[npeaks] - beats[npeaks - 1]
indexrr += 1
if indexrr == init_ecg:
indexrr = 0
elif dx[f] < 3. * np.median(qrspeakbuffer):
beats += [int(f) + bpsi]
else:
continue
npeaks += 1
qrspeakbuffer[indexqrs] = dx[f]
peak_idx_test[indexqrs] = f
indexqrs += 1
if indexqrs == init_ecg:
indexqrs = 0
if dx[f] <= DT:
# 4 - not valid
# 5 - If no QRS has been detected within 1.5 R-to-R intervals,
# there was a peak that was larger than half the detection threshold,
# and the peak followed the preceding detection by at least 360 ms,
# classify that peak as a QRS complex
tf = f + bpsi
# RR interval median
RRM = np.median(rrinterval) # initial values are good?
if len(beats) >= 2:
elapsed = tf - beats[npeaks - 1]
if elapsed >= 1.5 * RRM and elapsed > TH_elapsed:
if dx[f] > 0.5 * DT:
beats += [int(f) + offset]
# RR INTERVALS
if npeaks > 0:
rrinterval[indexrr] = beats[npeaks] - beats[npeaks
- 1]
indexrr += 1
if indexrr == init_ecg:
indexrr = 0
npeaks += 1
qrspeakbuffer[indexqrs] = dx[f]
peak_idx_test[indexqrs] = f
indexqrs += 1
if indexqrs == init_ecg:
indexqrs = 0
else:
noisepeakbuffer[indexnoise] = dx[f]
noise_idx[indexnoise] = f
indexnoise += 1
if indexnoise == init_ecg:
indexnoise = 0
else:
noisepeakbuffer[indexnoise] = dx[f]
noise_idx[indexnoise] = f
indexnoise += 1
if indexnoise == init_ecg:
indexnoise = 0
# Update Detection Threshold
ANP = np.median(noisepeakbuffer)
AQRSP = np.median(qrspeakbuffer)
DT = ANP + 0.475 * (AQRSP - ANP)
beats = np.array(beats)
r_beats = []
thres_ch = 0.85
adjacency = 0.05 * sampling_rate
for i in beats:
error = [False, False]
if i - lim < 0:
window = signal[0:i + lim]
add = 0
elif i + lim >= length:
window = signal[i - lim:length]
add = i - lim
else:
window = signal[i - lim:i + lim]
add = i - lim
# meanval = np.mean(window)
w_peaks, _ = st.find_extrema(signal=window, mode='max')
w_negpeaks, _ = st.find_extrema(signal=window, mode='min')
zerdiffs = np.where(np.diff(window) == 0)[0]
w_peaks = np.concatenate((w_peaks, zerdiffs))
w_negpeaks = np.concatenate((w_negpeaks, zerdiffs))
pospeaks = sorted(zip(window[w_peaks], w_peaks), reverse=True)
negpeaks = sorted(zip(window[w_negpeaks], w_negpeaks))
try:
twopeaks = [pospeaks[0]]
except IndexError:
twopeaks = []
try:
twonegpeaks = [negpeaks[0]]
except IndexError:
twonegpeaks = []
# getting positive peaks
for i in range(len(pospeaks) - 1):
if abs(pospeaks[0][1] - pospeaks[i + 1][1]) > adjacency:
twopeaks.append(pospeaks[i + 1])
break
try:
posdiv = abs(twopeaks[0][0] - twopeaks[1][0])
except IndexError:
error[0] = True
# getting negative peaks
for i in range(len(negpeaks) - 1):
if abs(negpeaks[0][1] - negpeaks[i + 1][1]) > adjacency:
twonegpeaks.append(negpeaks[i + 1])
break
try:
negdiv = abs(twonegpeaks[0][0] - twonegpeaks[1][0])
except IndexError:
error[1] = True
# choosing type of R-peak
n_errors = sum(error)
try:
if not n_errors:
if posdiv > thres_ch * negdiv:
# pos noerr
r_beats.append(twopeaks[0][1] + add)
else:
# neg noerr
r_beats.append(twonegpeaks[0][1] + add)
elif n_errors == 2:
if abs(twopeaks[0][1]) > abs(twonegpeaks[0][1]):
# pos allerr
r_beats.append(twopeaks[0][1] + add)
else:
# neg allerr
r_beats.append(twonegpeaks[0][1] + add)
elif error[0]:
# pos poserr
r_beats.append(twopeaks[0][1] + add)
else:
# neg negerr
r_beats.append(twonegpeaks[0][1] + add)
except IndexError:
continue
rpeaks = sorted(list(set(r_beats)))
rpeaks = np.array(rpeaks, dtype='int')
return utils.ReturnTuple((rpeaks, ), ('rpeaks', ))
def engzee_segmenter(signal=None, sampling_rate=1000., threshold=0.48):
"""ECG R-peak segmentation algorithm.
Follows the approach by Engelse and Zeelenberg [EnZe79]_ with the
modifications by Lourenco *et al.* [LSLL12]_.
Parameters
----------
signal : array
Input filtered ECG signal.
sampling_rate : int, float, optional
Sampling frequency (Hz).
threshold : float, optional
Detection threshold.
Returns
-------
rpeaks : array
R-peak location indices.
References
----------
.. [EnZe79] W. Engelse and C. Zeelenberg, "A single scan algorithm for
QRS detection and feature extraction", IEEE Comp. in Cardiology,
vol. 6, pp. 37-42, 1979
.. [LSLL12] A. Lourenco, H. Silva, P. Leite, R. Lourenco and A. Fred,
"Real Time Electrocardiogram Segmentation for Finger Based ECG
Biometrics", BIOSIGNALS 2012, pp. 49-54, 2012
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
# algorithm parameters
changeM = int(0.75 * sampling_rate)
Miterate = int(1.75 * sampling_rate)
v250ms = int(0.25 * sampling_rate)
v1200ms = int(1.2 * sampling_rate)
v1500ms = int(1.5 * sampling_rate)
v180ms = int(0.18 * sampling_rate)
p10ms = int(np.ceil(0.01 * sampling_rate))
p20ms = int(np.ceil(0.02 * sampling_rate))
err_kill = int(0.01 * sampling_rate)
inc = 1
mmth = threshold
mmp = 0.2
# Differentiator (1)
y1 = [signal[i] - signal[i - 4] for i in range(4, len(signal))]
# Low pass filter (2)
c = [1, 4, 6, 4, 1, -1, -4, -6, -4, -1]
y2 = np.array([np.dot(c, y1[n - 9:n + 1]) for n in range(9, len(y1))])
y2_len = len(y2)
# vars
MM = mmth * max(y2[:Miterate]) * np.ones(3)
MMidx = 0
Th = np.mean(MM)
NN = mmp * min(y2[:Miterate]) * np.ones(2)
NNidx = 0
ThNew = np.mean(NN)
update = False
nthfpluss = []
rpeaks = []
# Find nthf+ point
while True:
# If a previous intersection was found, continue the analysis from there
if update:
if inc * changeM + Miterate < y2_len:
a = (inc - 1) * changeM
b = inc * changeM + Miterate
Mnew = mmth * max(y2[a:b])
Nnew = mmp * min(y2[a:b])
elif y2_len - (inc - 1) * changeM > v1500ms:
a = (inc - 1) * changeM
Mnew = mmth * max(y2[a:])
Nnew = mmp * min(y2[a:])
if len(y2) - inc * changeM > Miterate:
MM[MMidx] = Mnew if Mnew <= 1.5 * MM[MMidx - 1] else 1.1 * MM[
MMidx - 1]
NN[NNidx] = Nnew if abs(Nnew) <= 1.5 * abs(
NN[NNidx - 1]) else 1.1 * NN[NNidx - 1]
MMidx = np.mod(MMidx + 1, len(MM))
NNidx = np.mod(NNidx + 1, len(NN))
Th = np.mean(MM)
ThNew = np.mean(NN)
inc += 1
update = False
if nthfpluss:
lastp = nthfpluss[-1] + 1
if lastp < (inc - 1) * changeM:
lastp = (inc - 1) * changeM
y22 = y2[lastp:inc * changeM + err_kill]
# find intersection with Th
try:
nthfplus = np.intersect1d(
np.nonzero(y22 > Th)[0],
np.nonzero(y22 < Th)[0] - 1)[0]
except IndexError:
if inc * changeM > len(y2):
break
else:
update = True
continue
# adjust index
nthfplus += int(lastp)
# if a previous R peak was found:
if rpeaks:
# check if intersection is within the 200-1200 ms interval. Modification: 300 ms -> 200 bpm
if nthfplus - rpeaks[-1] > v250ms and nthfplus - rpeaks[
-1] < v1200ms:
pass
# if new intersection is within the <200ms interval, skip it. Modification: 300 ms -> 200 bpm
elif nthfplus - rpeaks[-1] < v250ms:
nthfpluss += [nthfplus]
continue
# no previous intersection, find the first one
else:
try:
aux = np.nonzero(
y2[(inc - 1) * changeM:inc * changeM + err_kill] > Th)[0]
bux = np.nonzero(y2[
(inc - 1) * changeM:inc * changeM + err_kill] < Th)[0] - 1
nthfplus = int(
(inc - 1) * changeM) + np.intersect1d(aux, bux)[0]
except IndexError:
if inc * changeM > len(y2):
break
else:
update = True
continue
nthfpluss += [nthfplus]
# Define 160ms search region
windowW = np.arange(nthfplus, nthfplus + v180ms)
# Check if the condition y2[n] < Th holds for a specified
# number of consecutive points (experimentally we found this number to be at least 10 points)"
i, f = windowW[0], windowW[-1] if windowW[-1] < len(y2) else -1
hold_points = np.diff(np.nonzero(y2[i:f] < ThNew)[0])
cont = 0
for hp in hold_points:
if hp == 1:
cont += 1
if cont == p10ms - 1: # -1 is because diff eats a sample
max_shift = p20ms # looks for X's max a bit to the right
if nthfpluss[-1] > max_shift:
rpeaks += [
np.argmax(signal[i - max_shift:f]) + i - max_shift
]
else:
rpeaks += [np.argmax(signal[i:f]) + i]
break
else:
cont = 0
rpeaks = sorted(list(set(rpeaks)))
rpeaks = np.array(rpeaks, dtype='int')
return utils.ReturnTuple((rpeaks, ), ('rpeaks', ))
def christov_segmenter(signal=None, sampling_rate=1000.):
"""ECG R-peak segmentation algorithm.
Follows the approach by Christov [Chri04]_.
Parameters
----------
signal : array
Input filtered ECG signal.
sampling_rate : int, float, optional
Sampling frequency (Hz).
Returns
-------
rpeaks : array
R-peak location indices.
References
----------
.. [Chri04] Ivaylo I. Christov, "Real time electrocardiogram QRS
detection using combined adaptive threshold", BioMedical Engineering
OnLine 2004, vol. 3:28, 2004
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
length = len(signal)
# algorithm parameters
v100ms = int(0.1 * sampling_rate)
v50ms = int(0.050 * sampling_rate)
v300ms = int(0.300 * sampling_rate)
v350ms = int(0.350 * sampling_rate)
v200ms = int(0.2 * sampling_rate)
v1200ms = int(1.2 * sampling_rate)
M_th = 0.4 # paper is 0.6
# Pre-processing
# 1. Moving averaging filter for power-line interference suppression:
# averages samples in one period of the powerline
# interference frequency with a first zero at this frequency.
b = np.ones(int(0.02 * sampling_rate)) / 50.
a = [1]
X = ss.filtfilt(b, a, signal)
# 2. Moving averaging of samples in 28 ms interval for electromyogram
# noise suppression a filter with first zero at about 35 Hz.
b = np.ones(int(sampling_rate / 35.)) / 35.
X = ss.filtfilt(b, a, X)
X, _, _ = st.filter_signal(signal=X,
ftype='butter',
band='lowpass',
order=7,
frequency=40.,
sampling_rate=sampling_rate)
X, _, _ = st.filter_signal(signal=X,
ftype='butter',
band='highpass',
order=7,
frequency=9.,
sampling_rate=sampling_rate)
k, Y, L = 1, [], len(X)
for n in range(k + 1, L - k):
Y.append(X[n]**2 - X[n - k] * X[n + k])
Y = np.array(Y)
Y[Y < 0] = 0
# Complex lead
# Y = abs(scipy.diff(X)) # 1-lead
# 3. Moving averaging of a complex lead (the sintesis is
# explained in the next section) in 40 ms intervals a filter
# with first zero at about 25 Hz. It is suppressing the noise
# magnified by the differentiation procedure used in the
# process of the complex lead sintesis.
b = np.ones(int(sampling_rate / 25.)) / 25.
Y = ss.lfilter(b, a, Y)
# Init
MM = M_th * np.max(Y[:int(5 * sampling_rate)]) * np.ones(5)
MMidx = 0
M = np.mean(MM)
slope = np.linspace(1.0, 0.6, int(sampling_rate))
Rdec = 0
R = 0
RR = np.zeros(5)
RRidx = 0
Rm = 0
QRS = []
Rpeak = []
current_sample = 0
skip = False
F = np.mean(Y[:v350ms])
# Go through each sample
while current_sample < len(Y):
if QRS:
# No detection is allowed 200 ms after the current one. In
# the interval QRS to QRS+200ms a new value of M5 is calculated: newM5 = 0.6*max(Yi)
if current_sample <= QRS[-1] + v200ms:
Mnew = M_th * max(Y[QRS[-1]:QRS[-1] + v200ms])
# The estimated newM5 value can become quite high, if
# steep slope premature ventricular contraction or artifact
# appeared, and for that reason it is limited to newM5 = 1.1*M5 if newM5 > 1.5* M5
# The MM buffer is refreshed excluding the oldest component, and including M5 = newM5.
Mnew = Mnew if Mnew <= 1.5 * MM[MMidx -
1] else 1.1 * MM[MMidx - 1]
MM[MMidx] = Mnew
MMidx = np.mod(MMidx + 1, 5)
# M is calculated as an average value of MM.
Mtemp = np.mean(MM)
M = Mtemp
skip = True
# M is decreased in an interval 200 to 1200 ms following
# the last QRS detection at a low slope, reaching 60 % of its
# refreshed value at 1200 ms.
elif current_sample >= QRS[-1] + v200ms and current_sample < QRS[
-1] + v1200ms:
M = Mtemp * slope[current_sample - QRS[-1] - v200ms]
# After 1200 ms M remains unchanged.
# R = 0 V in the interval from the last detected QRS to 2/3 of the expected Rm.
if current_sample >= QRS[-1] and current_sample < QRS[-1] + (
2 / 3.) * Rm:
R = 0
# In the interval QRS + Rm * 2/3 to QRS + Rm, R decreases
# 1.4 times slower then the decrease of the previously discussed
# steep slope threshold (M in the 200 to 1200 ms interval).
elif current_sample >= QRS[-1] + (
2 / 3.) * Rm and current_sample < QRS[-1] + Rm:
R += Rdec
# After QRS + Rm the decrease of R is stopped
# MFR = M + F + R
MFR = M + F + R
# QRS or beat complex is detected if Yi = MFR
if not skip and Y[current_sample] >= MFR:
QRS += [current_sample]
Rpeak += [QRS[-1] + np.argmax(Y[QRS[-1]:QRS[-1] + v300ms])]
if len(QRS) >= 2:
# A buffer with the 5 last RR intervals is updated at any new QRS detection.
RR[RRidx] = QRS[-1] - QRS[-2]
RRidx = np.mod(RRidx + 1, 5)
skip = False
# With every signal sample, F is updated adding the maximum
# of Y in the latest 50 ms of the 350 ms interval and
# subtracting maxY in the earliest 50 ms of the interval.
if current_sample >= v350ms:
Y_latest50 = Y[current_sample - v50ms:current_sample]
Y_earliest50 = Y[current_sample - v350ms:current_sample - v300ms]
F += (max(Y_latest50) - max(Y_earliest50)) / 1000.
# Rm is the mean value of the buffer RR.
Rm = np.mean(RR)
current_sample += 1
rpeaks = []
for i in Rpeak:
a, b = i - v100ms, i + v100ms
if a < 0:
a = 0
if b > length:
b = length
rpeaks.append(np.argmax(signal[a:b]) + a)
rpeaks = sorted(list(set(rpeaks)))
rpeaks = np.array(rpeaks, dtype='int')
return utils.ReturnTuple((rpeaks, ), ('rpeaks', ))
def ssf_segmenter(signal=None,
sampling_rate=1000.,
threshold=20,
before=0.03,
after=0.01):
"""ECG R-peak segmentation based on the Slope Sum Function (SSF).
Parameters
----------
signal : array
Input filtered ECG signal.
sampling_rate : int, float, optional
Sampling frequency (Hz).
threshold : float, optional
SSF threshold.
before : float, optional
Search window size before R-peak candidate (seconds).
after : float, optional
Search window size after R-peak candidate (seconds).
Returns
-------
rpeaks : array
R-peak location indices.
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
# convert to samples
winB = int(before * sampling_rate)
winA = int(after * sampling_rate)
Rset = set()
length = len(signal)
# diff
dx = np.diff(signal)
dx[dx >= 0] = 0
dx = dx**2
# detection
idx, = np.nonzero(dx > threshold)
idx0 = np.hstack(([0], idx))
didx = np.diff(idx0)
# search
sidx = idx[didx > 1]
for item in sidx:
a = item - winB
if a < 0:
a = 0
b = item + winA
if b > length:
continue
r = np.argmax(signal[a:b]) + a
Rset.add(r)
# output
rpeaks = list(Rset)
rpeaks.sort()
rpeaks = np.array(rpeaks, dtype='int')
return utils.ReturnTuple((rpeaks, ), ('rpeaks', ))
def ecg(signal=None,
sampling_rate=1000,
show=True,
corr_rpeaks=True,
calc_heartrate=False):
"""Process a raw ECG signal and extract relevant signal features using
default parameters.
Parameters
----------
signal : array
Raw ECG signal.
sampling_rate : int, float, optional
Sampling frequency (Hz).
show : bool, optional
If True, show a summary plot.
Returns
-------
ts : array
Signal time axis reference (seconds).
filtered : array
Filtered ECG signal.
rpeaks : array
R-peak location indices.
templates_ts : array
Templates time axis reference (seconds).
templates : array
Extracted heartbeat templates.
heart_rate_ts : array
Heart rate time axis reference (seconds).
heart_rate : array
Instantaneous heart rate (bpm).
"""
# check inputs
if signal is None:
raise TypeError("Please specify an input signal.")
# ensure numpy
signal = np.array(signal)
sampling_rate = float(sampling_rate)
# filter signal
order = int(0.3 * sampling_rate)
filtered, _, _ = st.filter_signal(signal=signal,
ftype='FIR',
band='bandpass',
order=order,
frequency=[3, 45],
sampling_rate=sampling_rate)
# segment
rpeaks, = hamilton_segmenter(signal=filtered, sampling_rate=sampling_rate)
# get time vectors
length = len(signal)
T = (length - 1) / sampling_rate
ts = np.linspace(0, T, length, endpoint=True)
if corr_rpeaks:
# correct R-peak locations
rpeaks, = correct_rpeaks(signal=filtered,
rpeaks=rpeaks,
sampling_rate=sampling_rate,
tol=0.05)
if calc_heartrate:
# extract templates
templates, rpeaks = extract_heartbeats(signal=filtered,
rpeaks=rpeaks,
sampling_rate=sampling_rate,
before=0.2,
after=0.4)
# compute heart rate
hr_idx, hr = st.get_heart_rate(beats=rpeaks,
sampling_rate=sampling_rate,
smooth=True,
size=3)
#get time vectors
ts_hr = ts[hr_idx]
ts_tmpl = np.linspace(-0.2, 0.4, templates.shape[1], endpoint=False)
# plot
if show:
plotting.plot_ecg(ts=ts,
raw=signal,
filtered=filtered,
rpeaks=rpeaks,
templates_ts=ts_tmpl,
templates=templates,
heart_rate_ts=ts_hr,
heart_rate=hr,
path=None,
show=True)
# output
if calc_heartrate:
args = (ts, filtered, rpeaks, ts_tmpl, templates, ts_hr, hr)
names = ('ts', 'filtered', 'rpeaks', 'templates_ts', 'templates',
'heart_rate_ts', 'heart_rate')
return utils.ReturnTuple(args, names)
else:
args = (ts, filtered, rpeaks)
names = ('ts', 'filtered', 'rpeaks')
return utils.ReturnTuple(args, names)
def compare_segmentation(reference=None,
test=None,
sampling_rate=1000.,
offset=0,
minRR=None,
tol=0.05):
"""Compare the segmentation performance of a list of R-peak positions
against a reference list.
Parameters
----------
reference : array
Reference R-peak location indices.
test : array
Test R-peak location indices.
sampling_rate : int, float, optional
Sampling frequency (Hz).
offset : int, optional
Constant a priori offset (number of samples) between reference and
test R-peak locations.
minRR : float, optional
Minimum admissible RR interval (seconds).
tol : float, optional
Tolerance between corresponding reference and test R-peak
locations (seconds).
Returns
-------
TP : int
Number of true positive R-peaks.
FP : int
Number of false positive R-peaks.
performance : float
Test performance; TP / len(reference).
acc : float
Accuracy rate; TP / (TP + FP).
err : float
Error rate; FP / (TP + FP).
match : list
Indices of the elements of 'test' that match to an R-peak
from 'reference'.
deviation : array
Absolute errors of the matched R-peaks (seconds).
mean_deviation : float
Mean error (seconds).
std_deviation : float
Standard deviation of error (seconds).
mean_ref_ibi : float
Mean of the reference interbeat intervals (seconds).
std_ref_ibi : float
Standard deviation of the reference interbeat intervals (seconds).
mean_test_ibi : float
Mean of the test interbeat intervals (seconds).
std_test_ibi : float
Standard deviation of the test interbeat intervals (seconds).
"""
# check inputs
if reference is None:
raise TypeError("Please specify an input reference list of R-peak \
locations.")
if test is None:
raise TypeError("Please specify an input test list of R-peak \
locations.")
if minRR is None:
minRR = np.inf
sampling_rate = float(sampling_rate)
# ensure numpy
reference = np.array(reference)
test = np.array(test)
# convert to samples
minRR = minRR * sampling_rate
tol = tol * sampling_rate
TP = 0
FP = 0
matchIdx = []
dev = []
for i, r in enumerate(test):
# deviation to closest R in reference
ref = reference[np.argmin(np.abs(reference - (r + offset)))]
error = np.abs(ref - (r + offset))
if error < tol:
TP += 1
matchIdx.append(i)
dev.append(error)
else:
if len(matchIdx) > 0:
bdf = r - test[matchIdx[-1]]
if bdf < minRR:
# false positive, but removable with RR interval check
pass
else:
FP += 1
else:
FP += 1
# convert deviations to time
dev = np.array(dev, dtype='float')
dev /= sampling_rate
nd = len(dev)
if nd == 0:
mdev = np.nan
sdev = np.nan
elif nd == 1:
mdev = np.mean(dev)
sdev = 0.
else:
mdev = np.mean(dev)
sdev = np.std(dev, ddof=1)
# interbeat interval
th1 = 1.5 # 40 bpm
th2 = 0.3 # 200 bpm
rIBI = np.diff(reference)
rIBI = np.array(rIBI, dtype='float')
rIBI /= sampling_rate
good = np.nonzero((rIBI < th1) & (rIBI > th2))[0]
rIBI = rIBI[good]
nr = len(rIBI)
if nr == 0:
rIBIm = np.nan
rIBIs = np.nan
elif nr == 1:
rIBIm = np.mean(rIBI)
rIBIs = 0.
else:
rIBIm = np.mean(rIBI)
rIBIs = np.std(rIBI, ddof=1)
tIBI = np.diff(test[matchIdx])
tIBI = np.array(tIBI, dtype='float')
tIBI /= sampling_rate
good = np.nonzero((tIBI < th1) & (tIBI > th2))[0]
tIBI = tIBI[good]
nt = len(tIBI)
if nt == 0:
tIBIm = np.nan
tIBIs = np.nan
elif nt == 1:
tIBIm = np.mean(tIBI)
tIBIs = 0.
else:
tIBIm = np.mean(tIBI)
tIBIs = np.std(tIBI, ddof=1)
# output
perf = float(TP) / len(reference)
acc = float(TP) / (TP + FP)
err = float(FP) / (TP + FP)
args = (TP, FP, perf, acc, err, matchIdx, dev, mdev, sdev, rIBIm, rIBIs,
tIBIm, tIBIs)
names = (
'TP',
'FP',
'performance',
'acc',
'err',
'match',
'deviation',
'mean_deviation',
'std_deviation',
'mean_ref_ibi',
'std_ref_ibi',
'mean_test_ibi',
'std_test_ibi',
)
return utils.ReturnTuple(args, names)
