从xts对象获取日期列

Question

我曾经getSymbols获得股票数据,它返回的内容如下:

> require(quantmod)
> getSymbols(AAPL)
> head(AAPL)
           AAPL.Open AAPL.High AAPL.Low AAPL.Close
2007-01-03     86.29     86.58    81.90      83.80
2007-01-04     84.05     85.95    83.82      85.66
2007-01-05     85.77     86.20    84.40      85.05
2007-01-08     85.96     86.53    85.28      85.47
2007-01-09     86.45     92.98    85.15      92.57
2007-01-10     94.75     97.80    93.45      97.00
> str(AAPL)
An ‘xts’ object on 2007-01-03/2015-02-23 containing:
  Data: num [1:2049, 1:6] 86.3 84 85.8 86 86.5 ...
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:6] "AAPL.Open" "AAPL.High" "AAPL.Low" "AAPL.Close" ...
  Indexed by objects of class: [Date] TZ: UTC
  xts Attributes:  
List of 2
 $ src    : chr "yahoo"
 $ updated: POSIXct[1:1], format: "2015-02-24 17:12:45"

我如何获得日期？似乎日期不在数据中.AAPL[1,1]收益:

           AAPL.Open
2009-01-02     85.88

并rownames(AAPL)返回NULL.这里发生了什么？如何将日期与对象的其余部分相关联？我如何获得日期？

Answer 1

getSymbolsdata.frame默认情况下不返回; 它返回一个xts对象.xts对象没有行名.它们具有您可以使用该index函数访问的索引属性.