[R] Differential problem
Raphaëlle Carraud
raphaelle.carraud at oc-metalchem.com
Thu Jul 11 13:53:29 CEST 2013
Sorry for the bug, I had eliminated some lines to avoid making the program too big. Here is the version that works :
reaction<-function(z, state, dval, parameters) {
with(as.list(c(state)),{
# rate of change
Tr <- 273+90
P <- 0.98*10^5
K2 <- 10^(2993/Tr-9.226)*(10^-3)
K3 <- 10^(2072/Tr-7.234)*(10^-3)
K4 <- 10^(-20.83/Tr-0.5012)
K5 <- 10^(-965.5/Tr-1.481)
k1 <- (10^(652.1/Tr-0.7356))*(8.314*Tr/P)^2
kf2 <- 1.4*10^-33*(Tr/300)^(-3.8)*6.022*10^23*10^-6
kb2 <- kf2/K2*P/(8.314*Tr)
kf3 <- 3.1*10^-34*(Tr/300)^(-7.7)*10^(-6)*6.022*10^23
kb3 <- kf3/K3*P/(8.314*Tr)
kf4 <- 41
kf5 <- 0.25
r1 <- k1*A^2*H
r4 <- kf4*D*G - kf4/K4*E^2
r5 <- kf5*C*G - kf5/K5*E*I
res1 <- -dA + dB + 2*dC - 2*r1 - 2*r5 #
res2 <- dA + dD + r1 + r4 #
res3 <- K2 - C/B^2 #
res4 <- K3 - D/(A*B) #
res5 <- r5 + 2*r4 - dE #dHNO2/dz
res6 <- r5 -dI #dHNO3/dz
res7 <- -r5 - r4 - dG #dH2O/dz
res8 <- -r1/2 - dH #dO2/dz
list(c(res1, res2, res3, res4, res5, res6, res7, res8))
}) # end with(as.list ...
}
xi <- c(0.3, #x_NO
0.1, #x_NO2
0, #x_N2O4
0, #x_N2O3
0.05, #x_HNO2
0.05, #x_HNO3
0.2, #x_H2O
0.3) #x_O2
state <- c(A = xi[1]*Pt,
B = xi[2]*Pt,
C = xi[3]*Pt,
D = xi[4]*Pt,
E = xi[5]*Pt,
I = xi[6]*Pt,
G = xi[7]*Pt,
H = xi[8]*Pt)
dval <- c(dA = 1,
dB = 1,
dC = 0.5,
dD = 0.2,
dE = 0,
dI = 0,
dG = 0,
dH = 0)
parameters <- c(Pt = 0.98*10^5)
z <- seq(0, 1, by = 0.01) # en seconde
library(deSolve)
#out <- ode(y = state, times = z, func = reaction, parameters)
out <- daspk(y = state, dy = dval, times = z, res = reaction, parms = 0)
head(out)
plot(out)
I obtain the following message:
> library(deSolve)
> #out <- ode(y = state, times = z, func = reaction, parameters)
>
> out <- daspk(y = state, dy = dval, times = z, res = reaction, parms = 0)
Error in eval(expr, envir, enclos) : object 'dA' not found.
I tried adding the dval and parameters as you said:
with(as.list(c(state,dval,parameters)),{
I get the following message:
Warning messages:
1: In daspk(y = state, dy = dval, times = z, res = reaction, parms = 0) :
matrix of partial derivatives is singular with direct method-some equations redundant
2: In daspk(y = state, dy = dval, times = z, res = reaction, parms = 0) :
Returning early. Results are accurate, as far as they go
For the calling of the daspk function, I followed the documentation, where you have the same inversion:
daefun <- function(t, y, dy, parameters) {
+ res1 <- dy[1] + y[1] - y[2]
+ res2 <- y[2] * y[1] - t
+
+ list(c(res1, res2))
+ }
> library(deSolve)
> yini <- c(1, 0)
> dyini <- c(1, 0)
> times <- seq(0, 10, 0.1)
> ## solver
> system.time(out <- daspk(y = yini, dy = dyini, times = times, res = daefun, parms = 0))
Is it wrong? When I modify the order, I obtain again that object dA is not found, so I guessed the doc was right.
-----Message d'origine-----
De : Berend Hasselman [mailto:bhh at xs4all.nl]
Envoyé : jeudi 11 juillet 2013 12:33
À : Raphaëlle Carraud
Cc : r-help at r-project.org
Objet : Re: [R] Differential problem
On 11-07-2013, at 12:05, Raphaëlle Carraud <raphaelle.carraud at oc-metalchem.com> wrote:
> Sorry,
>
> Here is the program I have until now:
>
> reaction<-function(z, state, dval, parameters) {
> with(as.list(c(state)),{
>
> K2 <- 10^(2993/Tr-9.226)*(10^-3)
> K3 <- 10^(2072/Tr-7.234)*(10^-3)
> K4 <- 10^(-20.83/Tr-0.5012)
> K5 <- 10^(-965.5/Tr-1.481)
> k1 <- (10^(652.1/Tr-0.7356))*(8.314*Tr/P)^2
> kf2 <- 1.4*10^-33*(Tr/300)^(-3.8)*6.022*10^23*10^-6
> kb2 <- kf2/K2*P/(8.314*Tr)
> kf3 <- 3.1*10^-34*(Tr/300)^(-7.7)*10^(-6)*6.022*10^23
> kb3 <- kf3/K3*P/(8.314*Tr)
> kf4 <- 41
> kf5 <- 0.25
>
> r1 <- k1*A^2*H
> r4 <- kf4*D*G - kf4/K4*E^2
> r5 <- kf5*C*G - kf5/K5*E*I
>
> res1 <- -dA + dB + 2*dC - 2*r1 - 2*r5
> res2 <- dA + dD + r1 + r4
> res3 <- K2 - C/B^2
> res4 <- K3 - D/(A*B)
> res5 <- r5 + 2*r4 - dE
> res6 <- r5 -dI
> res7 <- -r5 - r4 - dG
> res8 <- -r1/2 - dH
>
> list(c(res1, res2, res3, res4, res5, res6, res7, res8))
> }) # end with(as.list ...
> }
>
> Ti <- 273+90 #K
> Pt <- 0.98*10^5 #Pa
>
> xi <- c(0.3, #x_NO
> 0.1, #x_NO2
> 0, #x_N2O4
> 0, #x_N2O3
> 0.05, #x_HNO2
> 0.05, #x_HNO3
> 0.2, #x_H2O
> 0.3) #x_O2
>
> state <- c(A = xi[1]*Pt,
> B = xi[2]*Pt,
> C = xi[3]*Pt,
> D = xi[4]*Pt,
> E = xi[5]*Pt,
> I = xi[6]*Pt,
> G = xi[7]*Pt,
> H = xi[8]*Pt)
>
> dval <- c(dA = 1,
> dB = 1,
> dC = 0.5,
> dD = 0.2,
> dE = 0,
> dI = 0,
> dG = 0,
> dH = 0)
>
> parameters <- c(Pt = 0.98*10^5)
>
> z <- seq(0, 1, by = 0.01)
>
> library(deSolve)
> out <- daspk(y = state, dy = dval, times = z, res = reaction, parms =
> 0)
> head(out)
> plot(out)
>
When I run this I get this error message:
Error in eval(expr, envir, enclos) : object 'Tr' not found
And shouldn't the first line of the reaction function be this
with(as.list(c(state,dval,parameters)),{
in stead of this
with(as.list(c(state)),{
The call of daspk also seems incorrect; shouldn't it be
out <- daspk(y = state, dy = dval, times = z, res = reaction, parms = parameters)
And finally: where does variable P come from? Not defined anywhere!
Berend
> -----Message d'origine-----
> De : Berend Hasselman [mailto:bhh at xs4all.nl] Envoyé : jeudi 11 juillet
> 2013 11:18 À : Raphaëlle Carraud Cc : r-help at r-project.org Objet : Re:
> [R] Differential problem
>
>
> On 11-07-2013, at 09:13, Raphaëlle Carraud <raphaelle.carraud at oc-metalchem.com> wrote:
>
>> Hello,
>>
>> I have the following differential equation system to solve, the variables I wish to obtain being A, B, C, D, E, I, G and H.
>>
>> 0 = -dA + dB + 2*dC - 2*r1 - 2*r5
>> 0 = dA + dD + r1 + r4
>> 0 = K2 - C/B^2
>> 0 = K3 - D/(A*B)
>>
>> 0 = r5 + 2*r4 - dE
>> 0 = r5 -dI
>> 0 = -r5 - r4 - dG
>> 0 = -r1/2 - dH
>>
>> r1, r4 and r5 are variables expressed as functions of A, B, C, D, I, G and H, calculated previously in the integrated function. K2 and K3 are parameters.
>>
>> As I have two algebraic equations, I think this system is a DAE (Algebraic differential equation). I found in the package deSolve two functions that resolve DAE but I didn't manage to obtain a solution; it says that the variable dA cannot be found.
>>
>
> Show us your script where you define the function and run the DAE solver. Without that nobody can provide an answer.
>
> Berend.
>
>> Does anyone know how to solve this problem?
>>
>> Thank you
>>
>> Raphaëlle Carraud
>>
>>
>> Raphaëlle Carraud
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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>
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