Thanks very much David for your answer. Sorry ! here is the code without the
error:
library(deSolve)
param <- c(a = 0.1, b = 1)
yini <- c(alpha0 = 6, beta0 = 2)
mod <- function(times, yini, param) {
with(as.list(c(yini, param)), {
gamma0 <- ifelse(times %in% seq(0,10,1), 5, 0)
## print(gamma0)
dalpha0 <- - a*alpha0 + gamma0
dbeta0 <- a*alpha0 - b*beta0
return(list(c(dalpha0, dbeta0)))
})}
times <- seq(from = 0, to = 10, by = 1/24)
out <- ode(func = mod, times = times, y = yini, parms = param)
plot(out, lwd = 2, xlab = "day")
Thanks in advance for your help!
Marine
________________________________
De : David Winsemius <dwinsem...@comcast.net>
Envoyé : vendredi 24 mars 2017 06:01
À : Marine Regis
Cc : r-help@r-project.org
Objet : Re: [R] How to change parameter values as a function to time with the
package "deSolve"
> On Mar 23, 2017, at 2:59 PM, Marine Regis <marine.re...@hotmail.fr> wrote:
>
> Hello,
>
> I am trying to solve an ODE in R using deSolve. With the following code, I
> expected the parameter �gamma0� takes the values 5 at time step 0, 1, 2, 3,
> 4, 5, 6, 7, 8, 9 and 10, and 0 otherwise. However, the print(gamma0) shows
> that �gamma0� stays at 0.
>
> Here is my ODE:
>
> param <- c(a = 0.1, b = 1)
> yini <- c(alpha0 = 0, beta0 = 0)
>
> mod <- function(times, yini, param) {
>
> with(as.list(c(yini, parameters)), {
>
> gamma0 <- ifelse(times %in% seq(0,10,1), 5, 0)
>
> # print(gamma0)
>
> dalpha0 <- - a*alpha0 + gamma0
> dbeta0 <- a*alpha0 - b*beta0
> return(list(c(dalpha0, dbeta0)))
>
> })}
>
> times <- seq(from = 0, to = 10, by = 1/24)
> out <- ode(func = mod, times = times, y = yini, parms = param)
> plot(out, lwd = 2, xlab = "day")
>
>
> What am I doing wrong? Thanks in advance for your help!
When I execute that code I get:
Error in as.list(c(yini, parameters)) : object 'parameters' not found
(The mistake seems fairly obvious when you look are the parameter list for your
`mod` function.)
Additionally: It's not generally good practice to use `with` inside functions,
but that's not the problem here.
--
David.
> Marine
>
>
> [[alternative HTML version deleted]]
>
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David Winsemius
Alameda, CA, USA
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