double ThresholdCurve::getROCArea(Instances &tcurve) {
const int n = tcurve.numInstances();
if (RELATION_NAME != tcurve.getRelationName() || (n == 0)) {
return std::numeric_limits<double>::quiet_NaN();
}
const int tpInd = tcurve.attribute(TRUE_POS_NAME).index();
const int fpInd = tcurve.attribute(FALSE_POS_NAME).index();
const double_array tpVals = tcurve.attributeToDoubleArray(tpInd);
const double_array fpVals = tcurve.attributeToDoubleArray(fpInd);
double area = 0.0, cumNeg = 0.0;
const double totalPos = tpVals[0];
const double totalNeg = fpVals[0];
for (int i = 0; i < n; i++) {
double cip, cin;
if (i < n - 1) {
cip = tpVals[i] - tpVals[i + 1];
cin = fpVals[i] - fpVals[i + 1];
}
else {
cip = tpVals[n - 1];
cin = fpVals[n - 1];
}
area += cip * (cumNeg + (0.5 * cin));
cumNeg += cin;
}
area /= (totalNeg * totalPos);
return area;
}
double ThresholdCurve::getNPointPrecision(Instances &tcurve, const int n) {
if (RELATION_NAME != tcurve.getRelationName() || (tcurve.numInstances() == 0)) {
return std::numeric_limits<double>::quiet_NaN();
}
int recallInd = tcurve.attribute(RECALL_NAME).index();
int precisInd = tcurve.attribute(PRECISION_NAME).index();
double_array recallVals = tcurve.attributeToDoubleArray(recallInd);
int_array sorted = Utils::Sort(recallVals);
double isize = 1.0 / (n - 1);
double psum = 0;
for (int i = 0; i < n; i++) {
int pos = binarySearch(sorted, recallVals, i * isize);
double recall = recallVals[sorted[pos]];
double precis = tcurve.instance(sorted[pos]).value(precisInd);
// interpolate figures for non-endpoints
while ((pos != 0) && (pos < sorted.size() - 1)) {
pos++;
double recall2 = recallVals[sorted[pos]];
if (recall2 != recall) {
double precis2 = tcurve.instance(sorted[pos]).value(precisInd);
double slope = (precis2 - precis) / (recall2 - recall);
double offset = precis - recall * slope;
precis = isize * i * slope + offset;
break;
}
}
psum += precis;
}
return psum / n;
}
int ThresholdCurve::getThresholdInstance(Instances &tcurve, const double threshold) {
if (RELATION_NAME != tcurve.getRelationName() || (tcurve.numInstances() == 0) || (threshold < 0) || (threshold > 1.0)) {
return -1;
}
if (tcurve.numInstances() == 1) {
return 0;
}
double_array tvals = tcurve.attributeToDoubleArray(tcurve.numAttributes() - 1);
int_array sorted = Utils::Sort(tvals);
return binarySearch(sorted, tvals, threshold);
}
