尝试使用desolve和bbmle从模型中提取参数：checkFunc（Func2，times，y，rho）中的错误

Question

我正在尝试获取一种物种B与另一种物种T的相互作用强度（a）。我对建模非常陌生，并且不太了解错误，因此详细的解释确实有帮助！

我的数据由变量day，densityT和densityB组成：

day = c（0,1,2,5,7,9,12,14,16,19,21,23,26,28,30,33,35）

密度T = c（10,11048,6550,10140,1106,1184,381,241,282,51,85,237,83,53,186,248,132）

密度B = c（0,0,0,0,15,120,579,568,105,511,224,632,275,107,6,0,0）

library(deSolve)
library(bbmle)
library(plotrix)
library(stats4)

r = 0.992 # Tetra parameter extracted from other code
    K = 6471 # Tetra parameter extracted from other code

    # density for Tetra (N1) and Bleph (N2)
    N1 = densityT
    N2 = densityB
    parameters <- c(a=0.1) # initial alpha parameter guess
    state <- c(N1 = densityT[1]) # initial condition

    t <- day 
    y.obs  <- densityT


    logistic <- function(times, state, parms) {
        with(as.list(c(state,parms)),{

        dNdt = r*N1*(1-(N1/K))-(a*N1*N2) 

        list(c(dNdt))
      }) 
    }

    shootfun <- function(a){
      out <- ode(y = state, times = t, func = logistic, parms = parameters, maxsteps = 100000)

      y.pred <- out[,2] 

      sigma  <- sqrt(sum((y.obs-y.pred)^2)/length(y.obs))

      nloglike <- -sum(dnorm(y.obs, mean = y.pred, sd = sigma,log = TRUE))
      return(nloglike)
    }

    shoot <- mle2(shootfun,start=list(a = parameters[1]),
                    method="Nelder-Mead", 
                    control = list(maxit = 100000, reltol = 1e-8, abstol = 1e-8))

    summary(shoot)

     **Error in checkFunc(Func2, times, y, rho) : 
      The number of derivatives returned by func() (18) must equal the length of the initial conditions vector (1)**