week 6 Flashcards
QRS Complex
a breakdown of parts of a ecg wave consists of:
PR interval
PR segment
QRS complex
QT segment
ST segment
atrial depolarization occurs during the…
PR interval
ventricle depolarization occurs during the…
QRS complex
ventricle repolarization occurs during the…
ST segment
when creating filters in matlab, N should be equal to
the length of the ECG wave
what construct can we use to calculate symmetrical/asymmetrical filters?
for loop
symmetrical filter for loop example
for i = 2:(N-1)
sym3(i-1) = (ECG(i-1) + ECG(i) + ECG(i+1))/3
end
asymmetrical filter for loop example
for i = 1:(N-2)
asym3(i) = mean(ECG(i:i+2))
end
3 classes of signal
periodic, aperiodic, step like (transient)
square wave in matlab
use square function!
looks like square humps
pulse train wave
small humps with wide gaps in between
sawtooth wave in matlab
use sawtooth function!
looks like backwards N
equation for sinusoidal wave form
x(t) = A sin(2 pi f t + 6)
A is the amplitude
f is the frequency
t is the period
6 is the phase
T = ?
(T is phase)
1/f
(f is frequency)
x(t) = ??
x(t + T)
t is time
T is period
how many periods is required to completely define a periodic signal?
1
periodic means that each phase is the same
aperiodic signal
exists over finite time frame but are zero before and after the time frame
aperiodic signals are treated as ____ with a period that approaches ____
periodic
infinity
operations can only be applied to ___ segments
non-zero
how do you average data with different lengths?
interpolate the data before averaging
transient signal
increases infinitely and doesn’t return to initial value, hardest to treat mathematically because any operation must be carried out to infinity
what is the best way to gain insight on a signal?
compare to reference signal or family of related reference signals
reference signals need to be…
known and not complex
ex: sin wav
correlation
quantitative comparison between two signals
correlation function in matlab
corrcoef(x, y)
correlation coefficient
number that signifies similarity between two signals, this number is between -1 and +1
crosscorrelation
correlating over many different time shifts or lags
lag
continuous variable of time used to shift x(t) with respect to y(t)
what is the result of crosscorrelation?
series of correlations between signals for different points in time.
like correlating x(t) and one second and y(t) at one second and storing that value, then doing it for two seconds and so on
