heartratevariability

 HeartRateVariability Analysis according to [1]

 X = heartratevariability(RRI [,units])
 X = heartratevariability(qrsindex [,Fs])
 X = heartratevariability(HDR)
 X = heartratevariability(HDR.EVENT)
 X = heartratevariability(filename)
 
 
 INPUT
   RRI     R-R-intervales [in seconds]
   HDR        as defined in the header structure of BioSig 
        and returned by QRS-detection
   filename     with event information
   Fs         sampling rate - used for conversion into time axis
   units    time units e.g. 'ms' (default: 's')  

 OUTPUT
   X          struct containing the results as defined by [1]
   X.meanRR          meanRR = meanNN
   X.SDRR        standard deviaation of RR intervales
   X.RMSSD           rmsSD = SDSD
     NN50count1
     NN50count2
     NN50count
    pNN50
    SD1        width of Poincar�plot; equivalent to sqrt(2)*RMSSD [2]
    SD2        length of Poincar�plot; i.e. 2SDRR�+SDSD�/2 [2]
    r_RR         correlation coefficient [2]
   X.VLF               power of very low frequency band (< 0.04 Hz)
   X.LF                power of low frequency band (0.04-0.15 Hz)
   X.HF                power of high low frequency band (0.15-0.4 Hz)
   X.TotalPower        power of high low frequency band (0.15-0.4 Hz)
   X.LFHFratio         LF/HF-ratio
   X.LFnu              normalized units of LF power (0.04-0.15 Hz)
   X.HFnu              normalized units of HF power  (0.15-0.4 Hz)

  semilogy(X.f,X.ASpectrum) shows the spectral density function  

 The spectral estimates are based on an autoregressive spectrum estimator 
 of the data which is oversampled by a factor of 4 using the Berger method.  
 The default model order is 15. In order to change these default settings, 
 change in the source code line 211 (oversampling factor) and/or 
 line 230 (order of the autoregressive model); 

 see also: QRSDETECT, BERGER, EVENTCODES.TXT

 Reference(s):
 [1] Heart Rate Variability
       Standards of Measurement, physilogcial interpretation and clinical use.
       Taskforce of the European Society for Cardiology and the North Americal Society of Pacing and Electrophysiology.
       European Heart Journal (1996) 17, 354-381.
 [2] M. Brennan, M.Palaniswami, P. Kamen
    Do Existing Measures of Poincar�Plot Geometriy Reflect Nonlinear Features of Heart Rate Variablilty?
    IEEE Trans Biomedical Eng. 48(11),2001,
 [3] U. Rajendra Acharya, K. Paul Joseph,N. Kannathal, Choo Min Lim, Jasjit S. Suri.
    Heart rate variability: a review.
    Med Bio Eng Comput (2006) 44:1031�1051