Counting Heartbeat with Arduino: Help with Code? Answered

I got a premade heartbeat sensor which uses an IR led and an IR receiver to sense heartbeat. It gives out an analog signal, which i have connected to my Arduino's A0 pin, and uploaded the analogRead sketch to it(sends values to serial port too).

Then to visualize the heartbeat i used a processing graph program that took the values from the serial port. When i place my finger on the sensor,  i get this graph shown below:  

Yes its very clear, but can anyone help me with the code? it just needs to measure the beats per minute, and store it in a variable. 

**The spike in the grph showing the pulse varies in height sometimes. So the code should calbrate and all. Also there is a 1-2 second delay before the clean pulse comes...