Matlab files

I've uploaded some matlab files. These basically answer question 4 in this problem set, but can easily be modified and used for other 2d problems, other solvers etc. They are as follows.

eulerstep.m % a forward Euler method for x'=Ax

beulerstep.m % a backward Euler method for x'=Ax

cnstep.m  % a  Crank-Nicholson method for x'=Ax

mysolve.m % uses the above routines to find approximate

                        trajctories

pportrait.m % graphical tool which uses mysolve to visualise  

                       phase portraits.