Specify the functions f₁,...,f_n
which make up the right hand side of the ode y' = f(t,y), f = (f₁,...,f_n)^T. They must have the structure f_i = f_i(t,y(1),...,y(n)). You must obey the FORTRAN conventions.
If for example n = 1 and the ode reads y'=y²+t then you write here:
  f(1)=y(1)**2 + t (remember the leading 6 blanks!)
(y(1) denotes the first component of y.)
You might use here variables i,j,k (e.g. for loops or counting), the logicals bool1, bool2 , bool3, a vector of 100 components v(.) , the variables h1,h2,h3,h4 (e.g. for intermediate calculations) which all are initialized with zero resp. false and the constants pi, e, sqrt2 (with their mathematical meaning).
f(1)=-4.d0*y(1)+y(1)*y(2)*0.1d0+3.d0*y(2) f(2)=1.d0*y(1)-2.d0*y(2)-0.1d0*y(1)*y(2)+0.1d0

Specify the integration interval:

a =

b =

Specify the initial values for y
This is a list of n numbers, separated by blank or comma.
1.0, -4.0

Select two components of y for plotting: index1=index2=1 is allowed

index1 =		Important index1 from 1,...,n !
index2 =		Important: index2 from 1,...,n !

select the integrator

	Euler/Euler modified
	Dormand - Prince (4/5) pair
	Rosenbrock-Wanner order 5
	RADAU5 (fully implict Runge-Kutta)

should the automatic stepsize selection be used?

	yes, stepsize automatic	select the precision wanted: tol = Important: 0 < tol < 1 ! Select the value smally an: smally = Important: smally > 0 ! select the maximum allowed stepsize hmax: hmax =
	no, fixed stepsize:	h = Important: h > 0 !

specify the number of subintervals which must be processed separately (length is a+i*(b-a)/num) an: 1 <= num <= 100. 1 means there are no fixed intermediate grid points.

Warning!!! - This may take some time.

Click on "evaluate", in order to submit your input.

back to the theory page