{ ### Input file: two columns, time of the R peak in seconds and beat type ### Ex.: 0.000 1 ### 0.808 1 ### 1.618 1 ### 2.458 1 CONVFMT = "%.3lf"; NN_min = .300; # NN intervals <= 0.3 s will be excluded NN_max = 1.800; # NN intervals >= 1.8 s will be excluded SF = 250; # ECG sampling frequency t = \$1; # Time of the R peak in seconds ann = \$2 # Annotation: beat type (1: sinus; 2: PVC; 3: PAC) #### The time of each R peak is rounded (up or down) to the closest multiple of 1/SF. #### Ex.: Let SF = 250 Hz (1/SF = 0.004 s). The time of each R peak should be multiples of 0.004 but sometimes it is not due to conversion/export problems. #### If, for example, the time of the R peak was 0.809, this value would be rounded down to 0.808. #### Users not interested in this "correction," should comment the next five lines. aux = int(sprintf(CONVFMT, t*SF)); if (t - aux/SF > 0.5) t = (aux+1)/SF; if (t - aux/SF <= 0.5 && t - aux/SF > 0) t = aux/SF; #### Calculation of NN and delta NN intervals after reading 4 data points NN = t - t_1; # Current NN interval NN_1 = t_1 - t_2; # Previous NN interval NN_2 = t_2 - t_3; # NN interval preceeding the "previous NN interval" dNN_formatted = sprintf(CONVFMT, t - 2*t_1 + t_2); # Current delta NN interval dNN = dNN_formatted + 0; dNN_1_formatted = sprintf(CONVFMT, t_1 - 2*t_2 + t_3); # Previous delta NN interval dNN_1 = dNN_1_formatted + 0; #### Verification of whether the current beat and the 3 preceeding ones are "normal sinus" beats (ann == 1) if (ann == 1 && ann_1 == 1 && ann_2 == 1 && ann_3 == 1) flag_1 = 0; else{ flag_1 = 1; non_sinus = 1; } if (NR <= 4 && (ann < 1 || ann_1 < 1 || ann_2 < 1 || ann_3 < 1)) non_sinus = 0; #### Verification of whether current NN interval and the 3 preceeding one are between NN_min (0.3 sec) and NN_max (1.8 sec) if (NN < NN_max && NN > NN_min && NN_1 < NN_max && NN_1 > NN_min && NN_2 < NN_max && NN_2 > NN_min) flag_2 = 0; else{ flag_2 = 1; outlier = 1; } if (NR <= 4 && (NN == 0 || NN_1 == 0 || NN_2 == 0 || NN_3 == 0)) outlier = 0; # Counter for the number of inflection points: IP # Counter for the number of delta NN intervals: n_dNN # Counter for the number of delta NN intervals in short (long) accelerative and decelerative segments: short (long) # Counter for the number of delta NN intervals between consecutive inflection points: cont #### Hard inflection point criterion: dNN_current * dNN_previous < 0. if (NR > 3 && flag_1 == 0 && flag_2 == 0 && dNN * dNN_1 < 0){ IP++; if (non_sinus != 1 && outlier != 1){ if (IP > 1) n_dNN += cont; if (cont <= 2 && IP > 1) short += cont; if (cont > 2 && IP > 1) long += cont; # print "Hard IP: time =", t_1, " \# Beat =", NR-2, " NN =", NN_1; if (IP == 1) NN_total = 1; else NN_total += cont; # print ("NN_total =", NN_total); } if(non_sinus == 1 || outlier == 1){ non_sinus = 0; outlier = 0; NN_total += 1 # print "Hard IP: time =", t_1, " \# Beat =", NR-2, " NN =", NN_1; # print "NN_total =", NN_total; } cont = 0; } #### Soft inflection point criterion: dNN * dNN_prev == 0 and dNN != dNN_prev if (NR > 3 && flag_1 == 0 && flag_2 == 0 && dNN * dNN_1 == 0 && dNN != dNN_1){ IP++; if (non_sinus != 1 && outlier != 1){ if (IP > 1) n_dNN += cont; if (dNN_1 != 0) if (cont <= 2 && IP > 1) short += cont; if (cont > 2 && IP > 1) long += cont; # print "Soft IP: time =", t_1, " \# Beat =", NR-2, " NN =", NN_1; if (IP == 1) NN_total = 1; else NN_total += cont; # print ("NN_total =", NN_total); } if((non_sinus == 1 || outlier == 1)){ non_sinus = 0; outlier = 0; NN_total += 1; # print "Soft IP: time =", t_1, " \# Beat =", NR-2, " NN =", NN_1; # print "NN_total =", NN_total; } cont = 0; } if (NR > 1) cont++; ann_3 = ann_2; ann_2 = ann_1; ann_1 = ann; t_3 = t_2; t_2 = t_1; t_1 = t; N_acc_dec = short + long; if (n_dNN > 0) PIP = (sprintf(CONVFMT,IP/NN_total*100)); if (N_acc_dec > 0) PNNSS = (sprintf(CONVFMT,short/N_acc_dec*100)); if (n_dNN > 0) PNNLS = (sprintf(CONVFMT,long/n_dNN*100)); } END{print "PIP =", IP"/"NN_total, "=", PIP";", " PNNSS =", short"/"N_acc_dec"*100 =", PNNSS";", " PNNLS =", long"/"n_dNN"*100 =", PNNLS}