optim函数参数缺失

Question

这是我的代码.该kum.loglik函数返回负对数似然,并采用两个参数a和b.我需要找到一个使用optim函数最小化此函数的a和b.(n1,n2,n3是预先指定的并传递给optim函数.

kum.loglik = function(a, b, n1, n2, n3) {
  loglik = n1*log(b*beta(1+2/a,b)) + n2 * log(b*beta(1+2/a,b)-2*b*beta(1+1/a,b)+1) +
    n3 * log(b*beta(1+1/a,b)-b*beta(1+2/a,b))
  return(-loglik)
}
optim(par=c(1,1), kum.loglik, method="L-BFGS-B",
      n1=n1, n2=n2, n3=n3,
      control=list(ndeps=c(5e-4,5e-4)))

此代码应该可以正常工作但它会给出错误消息

Error in b * beta(1 + 2/a, b) : 'b' is missing

这段代码有什么问题？

Answer 1

问题是(直接来自优化帮助):

fn: A function to be minimized (or maximized), with first
argument the vector of parameters over which minimization is
to take place.

你的kum.loglik函数需要带一个向量v拉出的向量,例如:

kum.loglik=function(v) { a = v[1]; b = v[2]; ...}