Analytics: minor fix to percentile computation

analytics/includes/CommonStatistics.h

@@ -97,8 +97,8 @@ void computePercentiles(std::vector<reading_t> &data, const std::vector<size_t>
     // Sorting the sensor reading buffer to extract quantiles
     std::sort(data.begin(), data.end(), [ ](const reading_t& lhs, const reading_t& rhs) { return lhs.value < rhs.value; });
     for(const auto& q : percentilePositions) {
-        idx = (data.size() * q) / 100;
-        mod = (data.size() * q) % 100;
+        idx = ((data.size()-1) * q) / 100;
+        mod = ((data.size()-1) * q) % 100;
         percentiles.push_back((mod==0 || idx==data.size()-1) ? data[idx].value : (data[idx].value + data[idx+1].value)/2);
     }
 }

analytics/operators/regressor/RegressorOperator.cpp

@@ -233,15 +233,13 @@ bool RegressorOperator::computeFeatureVector(U_Ptr unit) {
             std::sort(_buffer.begin(), _buffer.end(),
                       [](const reading_t &lhs, const reading_t &rhs) { return lhs.value < rhs.value; });
             // Computing 25th PERCENTILE
-            qId = (_buffer.size() * 25) / 100;
-            qMod = (_buffer.size() * 25) % 100;
-            _qtl25 = (qMod == 0 || qId == _buffer.size() - 1) ? _buffer[qId].value :
-                     (_buffer[qId].value + _buffer[qId + 1].value) / 2;
+            qId = ((_buffer.size()-1) * 25) / 100;
+            qMod = ((_buffer.size()-1) * 25) % 100;
+            _qtl25 = (qMod == 0 || qId == _buffer.size() - 1) ? _buffer[qId].value : (_buffer[qId].value + _buffer[qId + 1].value) / 2;
             // Computing 75th PERCENTILE
-            qId = (_buffer.size() * 75) / 100;
-            qMod = (_buffer.size() * 75) % 100;
-            _qtl75 = (qMod == 0 || qId == _buffer.size() - 1) ? _buffer[qId].value :
-                     (_buffer[qId].value + _buffer[qId + 1].value) / 2;
+            qId = ((_buffer.size()-1) * 75) / 100;
+            qMod = ((_buffer.size()-1) * 75) % 100;
+            _qtl75 = (qMod == 0 || qId == _buffer.size() - 1) ? _buffer[qId].value : (_buffer[qId].value + _buffer[qId + 1].value) / 2;
 
             fIdx = idx * REG_NUMFEATURES;
             // Casting and storing the statistical features