[R] deSolve - Function daspk on DAE system - Error

Vince vince.pileggi at ontario.ca
Sun Oct 2 05:20:10 CEST 2011


I'm getting this error on the attached code and breaking my head but can't
figure it out. Any help is much appreciated. Thanks, Vince

CODE:
library(deSolve)

Res_DAE=function(t, y, dy, pars) {
  with(as.list(c(y, dy, pars)), {
     
  res1 = -dS -dES-k2*ES
  res2 = -dP + k2*ES
 
  eq1 = Eo-E -ES
  eq2 = So-S -ES -P
  return(list(c(res1, res2, eq1, eq2)))
  })
}

pars <- c(Eo=0.02, So=0.02, k2=250, E=0.01); pars
yini <- c(S=0.01, ES = 0.01, P=0.0, E=0.01); yini
times <- seq(0, 0.01, by = 0.0001); times
dyini = c(dS=0.0, dES=0.0, dP=0.0)

## Tabular output check of matrix output

DAE <- daspk(y = yini, dy = dyini, times = times, res = Res_DAE, parms =
pars, atol = 1e-10, rtol = 1e-10)

ERROR:
daspk--  warning.. At T(=R1) and stepsize H (=R2) the      nonlinear solver
f
      nonlinear solver failed to converge      repeatedly of with abs (H) =
H
      repeatedly of with abs (H) = HMIN      preconditioner had repeated
failur
        0.0000000000000D+00  0.5960464477539D-14                                
Warning messages:
1: In daspk(y = yini, dy = dyini, times = times, res = Res_DAE, parms =
pars,  :
  repeated convergence test failures on a step - inaccurate Jacobian or
preconditioner?
2: In daspk(y = yini, dy = dyini, times = times, res = Res_DAE, parms =
pars,  :
  Returning early. Results are accurate, as far as they go

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