qrscorr

 Identification and correction of detection errors on QRS-beat sequences

 This algorithm identifies anomalies like FP, FN or ectopic beats.
  The FP and FN are corrected by deleting or inserting one or multiple beats.

 INPUT:
  QRSindex:     Sample values of the detected QRS-Complexes(minimum (8+(Nmax-1)Samples)
  Fs:           Sample Frequency
  Nmax:         Maximum number of insertions, deletions, movements at one position (default = 20)

 OUTPUT:
  QRStime_corr: Time values of the corrected QRS-Complexes
  dr:           Time values of the derivative of the original instantaneous
                 heart rate:
     dr = 2 * | (t(k-1) - 2t(k) + t(k+1)) / ((t(k-1) - t(k))*(t(k-1) - t(k+1))*(t(k) - t(k+1))) |
  dr_corr:      Time values of the derivative of the corrected instantaneous
                 heart rate:
  U:            Calculated threshold for dr (Umax = 0.5 [s-2])
  ANNOT:        Structure that annotates the corrected and uncorrected beats
  ANNOT:         ANNOT.ins: Time values of all inserted beats
                 ANNOT.del: Time values of all deleted beats
                 ANNOT.mov: Time values of all moved beats
                 ANNOT.NOR: Time values of all uncorrected beats


 [QRStime_corr,ANNOT] = qrscorr(QRSindex,Fs,Nmax);

 Example:
  [QRStime_corr,ANNOT] = qrscorr(QRSindex,256,15);


 Reference:
 [1] J. Mateo, P. Laguna, Analysis of Heart Rate Variability in Presence
      of Ectopic Beats Using the Heart Timing Signal
     IEEE Transactions on biomedical engineering,
      Vol.50, No.3, March 2003