向量中给定日期的最接近日期

我想在给定日期的向量中标识最接近的日期。假设我有以下日期向量（带有5个随机日期）：

I would like to identify the closest date in a vector of given date. Let's say I have the following date vector (with 5 random dates):

coldate= as.Date(c("2013-08-03", "2013-09-04", "2013-09-08", "2013-09-12", "2013-11-01"));

现在，我想找到最接近 x = as.Date的日期。 （ 2013-10-01）。

Now, I want to find the closest date to x = as.Date("2013-10-01") inside this vector.

这是我的代码：

> which((coldate-x) == min(coldate-x))
  [1] 1

结果应为4，因为日期 2013-09-12 是最接近的日期。但是，我有1 ...我的代码有什么问题？

The result should be 4, since the date "2013-09-12" is the closest. But, I have 1... What's wrong in my code?