levelcrossing

[UpCrossIndx, UpCrossTime, UpCrossValue, CrestIndx, CrestTime, CrestValue, TroughIndx, TroughTime, TroughValue, t] = levelcrossing(x, CrossingLevel, fs, dispout)

Description

Calculate crossing point for a given level by using an upward zero crossing method

Inputs

x

Input time series (oscillatory) data

CrossingLevel=mean(x);

Level that crossing reported for

If x is deterended wave (mean=0), then set CrossingLevel=0

fs=1;

Sampling frequency that data collected at in (Hz)

If fs is not given, then default fs is fs=1;

If fs=1, then index of data points represents time as well

dispout=’no’;

Define to display outputs or not (‘yes’: display, ‘no’: not display)

Outputs

UpCrossIndx

Index of up-crossing location

UpCrossTime

Time of up-crossing location (s)

UpCrossValue

Value of up-crossing

CrestIndx

Index of crest location

CrestTime

Time of wave crest location (s)

CrestValue

Value of wave crest

TroughIndx

Index of trough location

TroughTime

Time of wave trough location (s)

TroughValue

Value of wave trough

t

Time (s)

Examples

fs=2; %Sampling frequency
duration=1024; %Duration of the data
N=fs*duration; %Total number of points
df=fs/N; %Frequency difference
dt=1/fs; %Time difference, dt=1/fs
t(:,1)=linspace(0,duration-dt,N); %Time
x(:,1)=detrend(0.5.*cos(2*pi*0.2*t)+(-0.1+(0.1-(-0.1))).*rand(N,1));
[UpCrossIndx,UpCrossTime,UpCrossValue,CrestIndx,CrestTime,CrestValue,TroughIndx,TroughTime,TroughValue,t]=levelcrossing(x,mean(x),fs,'yes');

References