我用rvest包爬数据，但是结果是charater(0)，代码如下
> url = "http://data.2018.163.com/player_rank.html#/data/goals"
> web = read_html(url)
> players = web%>%
+   html_nodes(xpath = '//td[(((count(preceding-sibling::*) + 1) = 2) and parent::*)]//a')%>%html_text()
> players
character(0)
请问这是为什么，我弄了好几次都是这样