R语言数据输入你将用到a.txt文件中以下列的数据,“H“(hits),“HR”(home run),“AB”(at-bats).从现在开始以下的分析都限制在AB>=100和HR>=1的数据.请问这段话在R中如何实现?a.txt文件数据如下"entry","name","year","stint","teamID","lgID","G","AB","R","H","2B","3B","HR",...