问题
How do I subset an xts object to only include weekdays (Mon-Fri, with Saturday and Sunday excluded)?
回答1:
Here's what I'd do:
library(xts)
data(sample_matrix)
sample.xts <- as.xts(sample_matrix, descr='my new xts object')
x <- sample.xts['2007']
x[!weekdays(index(x)) %in% c("Saturday", "Sunday")]
EDIT:
Joshua Ulrich in comments points out a better solution using .indexwday(), one of a family of built-in accessor functions for extracting pieces of the index of xts class objects. Also, like Dirk Eddelbuettel's solution, the following should be locale-independent:
x[.indexwday(x) %in% 1:5]
回答2:
By computing the day-of-the week given the date, and subsetting. In the example, I use a Date type but the cast to POSIXlt works the same way for POSIXct intra-day timestamps.
> mydates <- Sys.Date() + 0:6
> mydates
[1] "2012-01-31" "2012-02-01" "2012-02-02" "2012-02-03" "2012-02-04"
+ "2012-02-05" "2012-02-06"
> we <- sapply(mydates, function(d) { as.POSIXlt(d)$wday}) %in% c(0, 6)
> we
[1] FALSE FALSE FALSE FALSE TRUE TRUE FALSE
> mydates[ ! we ]
[1] "2012-01-31" "2012-02-01" "2012-02-02" "2012-02-03" "2012-02-06"
>
This really is not an xts question but basic date handling.
来源：https://stackoverflow.com/questions/9088116/r-subset-xts-weekdays