CSV文件中的原始数据如下所示,即日期-时间格式为%Y%m%d,字母"T",后跟%H%m%S:
20151230T090029, 33.04
20151230T090029, 33.06
20151230T090029, 33.07
20151230T090029, 33.05
20151230T090029, 33.04
20151230T090029, 33.05
20151230T090029, 33.04
如何使第一列成为zoo或xts中的时间索引?
正如Josh O'Brien所建议的,您可以使用read.zoo
:
library(zoo)
Lines <- "20151230T090029, 33.04
20151230T090029, 33.06
20151230T090029, 33.07
20151230T090029, 33.05
20151230T090029, 33.04
20151230T090029, 33.05
20151230T090029, 33.04"
z <- read.zoo(text=Lines, sep=",", FUN=as.POSIXct, format="%Y%m%dT%H%M%S")
然后,您可以通过转换为xts并使用xts::make.index.unique
来处理Gabor提到的相同的时间戳问题。
library(xts)
x <- as.xts(z)
options(digits.secs=3)
(u <- make.index.unique(x, 0.001))
# [,1]
# 2015-12-30 09:00:29.000 33.04
# 2015-12-30 09:00:29.000 33.06
# 2015-12-30 09:00:29.001 33.07
# 2015-12-30 09:00:29.002 33.05
# 2015-12-30 09:00:29.003 33.04
# 2015-12-30 09:00:29.004 33.05
# 2015-12-30 09:00:29.005 33.04
请参阅R如何用分数秒格式化POSIXct,了解为什么分数秒的打印方式会使它们看起来不正确。
将数据设为d
:
> d
V1 V2
1 20151230T090029 33.04
2 20151230T090029 33.06
3 20151230T090029 33.07
4 20151230T090029 33.05
5 20151230T090029 33.04
6 20151230T090029 33.05
7 20151230T090029 33.04
然后可以使用注释中给出的格式字符串转换为POSIX时间类:
> as.POSIXct(d$V1,format="%Y%m%dT%H%M%S")
[1] "2015-12-30 09:00:29 GMT" "2015-12-30 09:00:29 GMT"
[3] "2015-12-30 09:00:29 GMT" "2015-12-30 09:00:29 GMT"
[5] "2015-12-30 09:00:29 GMT" "2015-12-30 09:00:29 GMT"
[7] "2015-12-30 09:00:29 GMT"
并构造了一个zoo
对象:
> zoo(d$V2, as.POSIXct(d$V1,format="%Y%m%dT%H%M%S"))
2015-12-30 09:00:29 2015-12-30 09:00:29 2015-12-30 09:00:29 2015-12-30 09:00:29
33.04 33.06 33.07 33.05
2015-12-30 09:00:29 2015-12-30 09:00:29 2015-12-30 09:00:29
33.04 33.05 33.04
Warning message:
In zoo(d$V2, as.POSIXct(d$V1, format = "%Y%m%dT%H%M%S")) :
some methods for “zoo” objects do not work if the index entries in ‘order.by’ are not unique
因为所有的时间点都是一样的。