diff --git a/ppg b/ppg
index 6bb2183..a14c1d7 100755
Binary files a/ppg and b/ppg differ
diff --git a/ppg.cpp b/ppg.cpp
index 5dc0601..a504d74 100644
--- a/ppg.cpp
+++ b/ppg.cpp
@@ -5,6 +5,25 @@
 
 int FPS = 15;
 int DISCARD_DURATION = 1;
+int BUFFER_DURATION = 1;
+
+template <typename T>
+cv::Mat plotGraph(std::vector<T>& vals, int YRange[2])
+{
+auto it = minmax_element(vals.begin(), vals.end());
+float scale = 1./ceil(*it.second - *it.first);
+float bias = *it.first;
+int rows = YRange[1] - YRange[0] + 1;
+cv::Mat image = 255*cv::Mat::ones( rows, vals.size(), CV_8UC3 );
+image.setTo(255);
+for (int i = 0; i < (int)vals.size()-1; i++)
+{
+cv::line(image, cv::Point(i, rows - 1 - (vals[i] -
+bias)*scale*YRange[1]), cv::Point(i+1, rows - 1 - (vals[i+1] -
+bias)*scale*YRange[1]), cv::Scalar(255, 0, 0), 1);
+}
+return image;
+}
 
 int main()
 {
@@ -65,10 +84,41 @@ int main()
 				foreheadROI.height *= 0.3;
 				
 				cv::rectangle(frame, foreheadROI, cv::Scalar(0, 0, 255), 1, 1, 0);
+				
+			cv::Mat frame_forehead = frame(foreheadROI);
+			cv::Scalar avg_forehead = mean(frame_forehead);
+			
+			bool isBufferFull = false;
+			int sampleIdBuffer = 0;
+			cv::Mat greenSignal(1, FPS*BUFFER_DURATION, CV_64F);
+			if (!isBufferFull)
+			{
+			greenSignal.at<double>(0, sampleIdBuffer) = avg_forehead[1] ;
+			sampleIdBuffer++;
+			if (sampleIdBuffer == FPS*BUFFER_DURATION)
+			{
+			isBufferFull = true;
+			}
+			}
+			
+			std::vector<double> greenSignalNormalized;
+			cv::Scalar mean, stddev;
+			cv::meanStdDev(greenSignal, mean, stddev);
+			for (int l_sample=0; l_sample < FPS*BUFFER_DURATION; l_sample++)
+			{
+				greenSignalNormalized.push_back((greenSignal.at<double>(0, l_sample) -
+				mean[0])/stddev[0]);
+			}
+			
+			int range[2] = {0, (int)(FPS*BUFFER_DURATION)};
+			cv::imshow("green", plotGraph(greenSignalNormalized, range));
+				
 		}
 		
 		
 		cv::imshow("Color", frame);
+		
+		
 			
 		if (cv::waitKey(1000.0/FPS) >= 0)
 			break;