Hi all,
Sorry for the re-post, I sent my previous e-mail before it was complete. I
am trying to model seroprevalence using the differential equation: dP/dt =
beta*seronegative*.001*(seropositive)-0.35*(0.999)*(seropositive)-r*seropositive.
I would like to estimate my two parameters, beta and r, using maximum
likelihood methods. I have included my code below:
summary=read.delim('summary.txt',header=T)
summary
Year N SeroPos SeroNeg
1 1 75 1 74
2 2 12 3 9
3 3 139 11 128
4 4 178 22 156
5 5 203 18 185
6 6 244 37 207
attach(summary)
poisNLL=function(P){
lambda=P[1]*SeroNeg*0.001*SeroPos-0.35*0.999*SeroPos-P[2]*SeroPos
v=-sum(dpois(SeroNeg,lambda=lambda,log=TRUE))
if (!is.finite(v)) v<- -2000000
v
}
opt1=optim(poisNLL,start=c(10,.1),method='BFGS')
I receive the following error from this code: "Error in optim(poisNLL, start
= c(10, 0.1), method = "BFGS") :
cannot coerce type 'closure' to vector of type 'double'"
Any assistance provided would be greatly appreciated!
Best,
Tyler
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