diff --git a/src/framebuffer.cpp b/src/framebuffer.cpp
--- a/src/framebuffer.cpp
+++ b/src/framebuffer.cpp
@@ -45,7 +45,7 @@ void FrameBuffer::resize(size_t size)
 
     for (int i = fill_start; i < int(size); i++)
     {
-        newData[i] = _sample(i - offset);
+        newData[i] = sample(i - offset);
     }
 
     // fill the beginning of the new data
@@ -141,17 +141,12 @@ size_t FrameBuffer::size() const
     return _size;
 }
 
-QPointF FrameBuffer::sample(size_t i) const
-{
-    return QPointF(i, _sample(i));
-}
-
 QRectF FrameBuffer::boundingRect() const
 {
     return _boundingRect;
 }
 
-double FrameBuffer::_sample(size_t i) const
+double FrameBuffer::sample(size_t i) const
 {
     size_t index = headIndex + i;
     if (index >= _size) index -= _size;
diff --git a/src/framebuffer.h b/src/framebuffer.h
--- a/src/framebuffer.h
+++ b/src/framebuffer.h
@@ -33,10 +33,10 @@ public:
     void addSamples(double* samples, size_t size);
     void clear(); // fill 0
 
-    // QwtSeriesData implementations
+    // QwtSeriesData related implementations
     size_t size() const;
-    QPointF sample(size_t i) const;
     QRectF boundingRect() const;
+    double sample(size_t i) const;
 
 private:
     size_t _size; // size of `data`
@@ -44,8 +44,6 @@ private:
     size_t headIndex; // indicates the actual `0` index of the ring buffer
 
     QRectF _boundingRect;
-
-    double _sample(size_t i) const;
 };
 
 #endif // FRAMEBUFFER_H
diff --git a/src/framebufferseries.cpp b/src/framebufferseries.cpp
--- a/src/framebufferseries.cpp
+++ b/src/framebufferseries.cpp
@@ -13,7 +13,7 @@ size_t FrameBufferSeries::size() const
 
 QPointF FrameBufferSeries::sample(size_t i) const
 {
-    return _buffer->sample(i);
+    return QPointF(i, _buffer->sample(i));
 }
 
 QRectF FrameBufferSeries::boundingRect() const
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -480,7 +480,7 @@ void MainWindow::onExportCsv()
             {
                 for (unsigned int ci = 0; ci < numOfChannels; ci++)
                 {
-                    fileStream << channelMan.channelBuffer(ci)->sample(i).y();
+                    fileStream << channelMan.channelBuffer(ci)->sample(i);
                     if (ci != numOfChannels-1) fileStream << ",";
                 }
                 fileStream << '\n';
diff --git a/src/snapshotmanager.cpp b/src/snapshotmanager.cpp
--- a/src/snapshotmanager.cpp
+++ b/src/snapshotmanager.cpp
@@ -73,7 +73,7 @@ void SnapshotManager::takeSnapshot()
         snapshot->data.append(QVector<QPointF>(numOfSamples));
         for (unsigned i = 0; i < numOfSamples; i++)
         {
-            snapshot->data[ci][i] = _channelMan->channelBuffer(ci)->sample(i);
+            snapshot->data[ci][i] = QPointF(i, _channelMan->channelBuffer(ci)->sample(i));
         }
     }