上节我们简单介绍了Dataframe的定义，这节我们具体来看一下Dataframe的操作
首先，数据框的创建函数为 data.frame( )，参考R语言的帮助文档，我们来了解一下data.frame( )的具体用法：
Usage data.frame(..., row.names = NULL, check.rows = FALSE, check.names = TRUE, fix.empty.names = TRUE, stringsAsFactors = default.stringsAsFactors()) default.stringsAsFactors() Arguments ... :these arguments are of either the form value or tag = value. Component names are created based on the tag (if present) or the deparsed argument itself. row.names :NULL or a single integer or character string specifying a column to be used as row names, or a character or integer vector giving the row names for the data frame.