From Setzer.Woodrow@epamail.epa.gov  Thu Feb  7 18:16:14 2002
From: Setzer.Woodrow@epamail.epa.gov (Setzer.Woodrow@epamail.epa.gov)
Date: Thu, 7 Feb 2002 19:16:14 +0100 (MET)
Subject: [Rd] typo and user-proofing in odesolve() (PR#1295)
Message-ID: <200202071816.TAA06457@pubhealth.ku.dk>

Forward to r-bugs to maintain a record.

R. Woodrow Setzer, Jr.                                            Phone:
(919) 541-0128
Experimental Toxicology Division                       Fax:  (919)
541-5394
Pharmacokinetics Branch
NHEERL MD-74; US EPA; RTP, NC 27711
----- Forwarded by Woodrow Setzer/RTP/USEPA/US on 02/04/02 08:53 AM
-----
                                                                                                                      
                    Woodrow Setzer                                                                                    
                                         To:     bolker@zoo.ufl.edu                                                   
                    02/01/02 03:23       cc:     owner-r-devel@stat.math.ethz.ch                                      
                    PM                   Subject:     Re: [Rd] typo and user-proofing in odesolve() (PR#1295)         
                                         (Document link: Woody Setzer)                                                
                                                                                                                      



Probably r-devel is not the right place for this discussion, since
odesolve is not an "official" part of R (not even a recommended
package).  I'll respond here to get it in the record, though.  I expect
to have a new release of odesolve ready in a couple of weeks.  lsoda
already calls func() once, to determine the number of "extra" values
returned; it was foolish of me not to test for the kind of value
returned at the same time.  That fix is already in the next release.
I'll see what other defensive checking can be done, as well.
Thanks for the spelling correction.

R. Woodrow Setzer, Jr.                                            Phone:
(919) 541-0128
Experimental Toxicology Division                       Fax:  (919)
541-5394
Pharmacokinetics Branch
NHEERL MD-74; US EPA; RTP, NC 27711


                                                                                                                              
                    bolker@zoo.ufl.edu                                                                                        
                    Sent by:                     To:     r-devel@stat.math.ethz.ch                                            
                    owner-r-devel@stat.ma        cc:                                                                          
                    th.ethz.ch                   Subject:     [Rd] typo and user-proofing in odesolve() (PR#1295)             
                                                                                                                              
                                                                                                                              
                    02/01/02 12:34 PM                                                                                         
                                                                                                                              
                                                                                                                              





  A couple of minor points about the odesolve package
(which I am otherwise enjoying very much):

 1. "scalar" is misspelled as "scaler" in the definitions of
the rtol and atol parameters

 2. it is possible to crash R by doing something dumb, e.g
failing to read the documentation carefully enough and (a)
returning only a vector of derivatives and not a list of
(derivatives, global values) and (b) making the derivative
vector shorter than the vector of initial conditions (see example
below).

  I know that this is my fault, but it might be possible/useful
to "user-proof" lsoda() some more (try func() once and see if
it returns a list of the appropriate form, check the derivative
vector for length matching the IC vector, etc ...

tderiv <- function(t,x,parms) {
#  return(list(c(x[1]*parms[1],x[2]*parms[2],parms[3]*(x[1]
+x[2])),NULL))
   return(c(x[1]*parms[1],x[2]*parms[2],parms[3]*(x[1]+x[2])))
}

lsoda(rep(1,2),c(0:20),tderiv,c(0.01,-0.01,1.2))


--please do not edit the information below--

Version:
 platform = i686-pc-linux-gnu
 arch = i686
 os = linux-gnu
 system = i686, linux-gnu
 status =
 major = 1
 minor = 3.1
 year = 2001
 month = 08
 day = 31
 language = R

Search Path:
 .GlobalEnv, package:ctest, Autoloads, package:base

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[Rd] typo and user-proofing in odesolve() (PR#1295)
Setzer.Woodrow@epamail.epa.gov