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Scilab Help >> Differential calculus, Integration > ode_root


ordinary differential equation solver with root finding

Calling Sequence

[y, rd, w, iw] = ode("root", y0, t0, t [,rtol [,atol]], f [,jac], ng, g [,w,iw])



a real vector or matrix (initial conditions).


a real scalar (initial time).


a real vector (times at which the solution is computed).


an external i.e. function or character string or list.

rtol, atol

a real constants or real vectors of the same size as y.


an external i.e. function or character string or list.

w, iw

a real vectors. (INPUT/OUTPUT)


an integer.


an external i.e. function or character string or list.


a real vector or matrix. (OUTPUT)


a real vector. (OUTPUT)


With this syntax (first argument equal to "root") ode computes the solution of the differential equation dy/dt=f(t,y) until the state y(t) crosses the surface g(t,y)=0.

g should give the equation of the surface. It is an external i.e. a function with specified syntax, or the name of a Fortran subroutine or a C function (character string) with specified calling sequence or a list.

If g is a function the syntax should be as follows:

z = g(t,y)

where t is a real scalar (time) and y a real vector (state). It returns a vector of size ng which corresponds to the ng constraints. If g is a character string it refers to the name of a Fortran subroutine or a C function, with the following calling sequence: g(n,t,y,ng,gout) where ng is the number of constraints and gout is the value of g (output of the program). If g is a list the same conventions as for f apply (see ode help).

Ouput rd is a 1 x k vector. The first entry contains the stopping time. Other entries indicate which components of g have changed sign. k larger than 2 indicates that more than one surface ((k-1) surfaces) have been simultaneously traversed.

Other arguments and other options are the same as for ode, see the ode help.


// Integration of the differential equation
// dy/dt=y , y(0)=1, and finds the minimum time t such that y(t)=2

See Also

  • dasrt — DAE solver with zero crossing
  • daskr — DAE solver with zero crossing
  • ode — ordinary differential equation solver
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<< ode_optional_output Differential calculus, Integration odedc >>

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Last updated:
Fri Apr 11 14:06:50 CEST 2014