# logistic equation x'=r*x*(1-x) # parameter par r=2.5 # initial condition init x=.2 # tell XPP it is a discrete equation @ meth=discrete # tell it to use 200 points @ total=200 doneType this file as an ASCII text file and save it. Or just grab it here. The lines starting with # are comments. Most everything can be changed from within the program. However, the dimensions, names, etc cannot be altered. The file is typed in pretty much the same way you would if you were writing the equations; XPP is too stupid to recognize spaces for multiplication, so you have to put the ``*'' sign between quantities. Functions such as am(V) are defined in the obvious fashion. Parameters are declared with the par statement. They can be separated by spaces or commas. The ``='' sign, the parameter name, and its starting value must have NO spaces between them.
THIS IS WRONG:
par gl = .3
THIS IS RIGHT:
Initial data can be defined with the init statement. Each file must end with a done statement. Any line that starts with a # is a comment and ignored.