Histogram implementation

histogramchart.h

@@ -0,0 +1,100 @@
+#ifndef HISTOGRAMCHART_H
+#define HISTOGRAMCHART_H
+
+#include <cmath>
+
+#include <QQuickItem>
+#include <QtQuick/QQuickPaintedItem>
+#include <QColor>
+
+
+struct Statistics {
+  qreal sum = 0;
+  qreal sumSquares = 0;
+  int count = 0;
+
+  void add(qreal v) {
+      sum += v;
+      sumSquares += v*v;
+      count++;
+  }
+
+  void clear() {
+    sum = 0;
+    sumSquares = 0;
+    count = 0;
+  }
+
+  int getCount() const {
+      return count;
+  }
+
+  qreal getMean() const {
+    return sum / static_cast<qreal>(count);
+  }
+
+  qreal getStdDev() const {
+    const qreal x = sumSquares / static_cast<qreal>(count);
+    const qreal e = getMean();
+    return std::sqrt(x - (e*e));
+  }
+};
+
+class HistogramChart : public QQuickPaintedItem
+{
+    Q_OBJECT
+    Q_PROPERTY(QString name READ name WRITE setName)
+    Q_PROPERTY(QColor color READ color WRITE setColor)
+    Q_PROPERTY(qreal  binWidth    READ binWidth WRITE setBinWidth)
+    Q_PROPERTY(qreal  mean        READ mean)
+    Q_PROPERTY(qreal  stdDev      READ stdDev)
+    Q_PROPERTY(int    totalCount  READ totalCount)
+    Q_PROPERTY(qreal  maxBinValue READ maxBinValue)
+
+public:
+    HistogramChart(QQuickItem* parent = nullptr);
+
+    QString name() const { return m_name; }
+    void setName(const QString &name) { m_name = name; }
+
+    QColor color() const { return m_color; }
+    void setColor(const QColor& color) { m_color = color; }
+
+    qreal binWidth() const { return _binWidth; }
+    void setBinWidth(qreal newBinWidth) { _binWidth = newBinWidth; reset(); }
+
+    qreal mean()        const { return stats.getMean();   }
+    qreal stdDev()      const { return stats.getStdDev(); }
+    int   totalCount()  const { return stats.getCount();  }
+    qreal maxBinValue() const { return maxBinIndex * binWidth(); }
+
+    void paint(QPainter *painter);
+
+    Q_INVOKABLE void pushData(qreal value);
+
+    Q_INVOKABLE void clear();  // soft reset
+    Q_INVOKABLE void reset();  // hard reset
+
+public:
+    int numberOfBins() const;
+    int binIndex(qreal value) const;
+
+
+private:
+    QString m_name;
+    QColor m_color;
+
+    std::vector<int> _histogram;
+    qreal _binWidth = 100;
+    qreal minValue = std::numeric_limits<qreal>::quiet_NaN();
+    qreal maxValue = std::numeric_limits<qreal>::quiet_NaN();
+
+    size_t lastUpdatedBinIndex = 0;
+    int maxBinCount = 0;
+    int maxBinIndex = 0;
+
+    // Satistics
+    Statistics stats;
+};
+
+#endif // HISTOGRAMCHART_H