If you want it to graph in real time that you can see, you'll need to figure out a display but that may be too much for the Arduino and still give you accurate readings.
A second processor would be better since you want a graphical output that you prob want to save as an image. Arduino can print the real time readings numerically to serial and you can feed that into a computer to graph. That software you need to find or write.
A Pi might be able to do it all in one.