Good graph plotting app [closed]

Does anyone know of a free graph plotting app for Windows (or an online tool) that can plot something like this?

Xn+1= r sin (π * Xn)


I'd like to suggest WolframAlpha, but it has trouble with the "r*". The best I could do is this.

enter image description here


I'd try Gnuplot or Octave/Matlab. If you had an Apple, the built-in Grapher would do the job.


See Science: Math: Software: Graphing for a few dozens of plotting applications.