无法将类型'closure'强制转换为类型'double'的向量

Question

我应该让以下函数从起始值0开始运行（以测试运行），但是在我应用optim（）的情况下，出现错误消息“无法将类型'closure'强制转换为类型'double'的向量”“ < / p>

这是我的代码：

log.likelihood(params, x, y)
logistic.fit(xtrain, ytrain)
logistic.predict(xtest, fit)

log.likelihood = function(params, x, y) {

    x = cbind(rep(1, nrow(x)), x) 
    Bx.sum = params %*% t(x) 
    t1 = sum((1-y)*Bx.sum) # 1st term
    t2 = sum(log(1+sapply(-Bx.sum, exp, simplify=T))) 

    likelihood = -(t1+t2)
    return(-likelihood)
}



optim(params = 0, x = xtrain, y = ytrain, log.likelihood, data, method='BFGS')