diff --git a/src/framebufferseries.h b/src/framebufferseries.h
--- a/src/framebufferseries.h
+++ b/src/framebufferseries.h
@@ -44,12 +44,16 @@ public:
     size_t size() const;
     QPointF sample(size_t i) const;
     QRectF boundingRect() const;
+    void setRectOfInterest(const QRectF& rect);
 
 private:
     FrameBuffer* _buffer;
     bool xAsIndex;
     double _xmin;
     double _xmax;
+
+    size_t int_index_start; ///< starting index of "rectangle of interest"
+    size_t int_index_end;   ///< ending index of "rectangle of interest"
 };
 
 #endif // FRAMEBUFFERSERIES_H