You may use turbo mode if you want immediate graphs. Press the flag, choose the amount of smoothing you want, and then press space. It will draw a smoothed line. Continue changing the variable and pressing space to explore levels of smoothing.
This program makes a random jittery graph, and then smooths it using an algorithm called the Moving Average Method, which replaces every point with the average of some number of points around it. The smoothing variable determines how many points it should take the average from.