chemreac.m

ode routines in matlab

function [out] = ChemReac(x, y, flag)
%
%  Evaluate the right hand side function for the
%  chemical reaction system
%
%    y_1'(x) = -k1*y_1(x) 
%    y_2'(x) =  k1*y_1(x) - k2*y_2(x)
%    y_3'(x) =              k2*y_2(x)
%
%
%

global k1 k2

switch( flag )
   case '' % return right hand side

      out  = [ -k1   0   0;
                k1  -k2  0;
                0    k2  0 ]* y;
   
   case 'jacobian' % return Jaacobian of right hand side

      out  = [ -k1   0   0;
                k1  -k2  0;
                0    k2  0 ];
   
   otherwise
      error(['Unknown request .'])
end