I think the command you want is:
if(t %in% feed_days) C_A <- 1.5 else C_A <- 0
Do not confuse `%in%` (which is essentially
"are the left-hand values in the right-hand
vector)
with
"in" of the `for` loop.
By the way,
if(t == TRUE)
is redundant -- better is:
if(t)
Pat
On 02/03/2013 23:57, Louise Stevenson wrote:
Hi,
I'm trying to set up R to run a simulation of two populations in which every 3.5 days,
the initial value of one of the populations is reset to 1.5. I'm simulation an experiment
we did in which we fed Daphnia populations twice a week with algae, so I want the initial
value of the algal population to reset to 1.5 twice a week to simulate that feeding. I've
use for loops and if/else loops before but I can't figure out how to syntax "if t is
in this vector of possible t values, do this command, else, do this command" if that
makes sense. Here's what I have (and it doesn't work):
params = c(1, 0.15, 0.164, 1)
init = c(1.5, 0.05)
t=seq(1,60, by=0.5) #all time values, experiment ran for 60 days
#feeding sequence - every "3.5 days"
feed_days = seq(1,60,by=3.5)
Daphnia <- function(t,x,params){
C_D = x[2];
C_A = 0;
for(t %in% feed_days){
if t == TRUE {
C_A = 1.5
}
else{
C_A = 0
}}
gamma = params[1]; m_D = params[2]; K_q = params[3]; q_max = params[4];
M_D = m_D * C_D
I_A = (C_D * q_max * C_A) / (K_q + C_A)
r_D = gamma * I_A
return(
list(c(
- I_A,
r_D - M_D
)))
}
library(deSolve)
results <- ode(init, t, Daphnia, params, method = "lsoda")
Let me know if there's any other info that would be helpful and thanks very
much for your help!
[[alternative HTML version deleted]]
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