{
### 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}