I have a vector of dates and for each entry, I would like to assign a season. So for example, if a date is between 21.12. and 21.3., I would says that's winter
. So far I have tried the following code but I couldn't make it more generic, irrespective of the year.
my.dates <- as.Date("2011-12-01", format = "%Y-%m-%d") + 0:60 low.date <- as.Date("2011-12-15", format = "%Y-%m-%d") high.date <- as.Date("2012-01-15", format = "%Y-%m-%d") my.dates[my.dates <= high.date & my.dates >= low.date] [1] "2011-12-15" "2011-12-16" "2011-12-17" "2011-12-18" "2011-12-19" "2011-12-20" "2011-12-21" "2011-12-22" "2011-12-23" "2011-12-24" "2011-12-25" [12] "2011-12-26" "2011-12-27" "2011-12-28" "2011-12-29" "2011-12-30" "2011-12-31" "2012-01-01" "2012-01-02" "2012-01-03" "2012-01-04" "2012-01-05" [23] "2012-01-06" "2012-01-07" "2012-01-08" "2012-01-09" "2012-01-10" "2012-01-11" "2012-01-12" "2012-01-13" "2012-01-14" "2012-01-15"
I have tried formatting the dates without the year, but it isn't working.
ld <- as.Date("12-15", format = "%m-%d") hd <- as.Date("01-15", format = "%m-%d") my.dates[my.dates <= hd & my.dates >= ld]
How about using something like this:
getSeason <- function(DATES) { WS <- as.Date("2012-12-15", format = "%Y-%m-%d") # Winter Solstice SE <- as.Date("2012-3-15", format = "%Y-%m-%d") # Spring Equinox SS <- as.Date("2012-6-15", format = "%Y-%m-%d") # Summer Solstice FE <- as.Date("2012-9-15", format = "%Y-%m-%d") # Fall Equinox # Convert dates from any year to 2012 dates d <- as.Date(strftime(DATES, format="2012-%m-%d")) ifelse (d >= WS | d < SE, "Winter", ifelse (d >= SE & d < SS, "Spring", ifelse (d >= SS & d < FE, "Summer", "Fall"))) } my.dates <- as.Date("2011-12-01", format = "%Y-%m-%d") + 0:60 head(getSeason(my.dates), 24) # [1] "Fall" "Fall" "Fall" "Fall" "Fall" "Fall" "Fall" # [8] "Fall" "Fall" "Fall" "Fall" "Fall" "Fall" "Fall" # [15] "Winter" "Winter" "Winter" "Winter" "Winter" "Winter"
One note: 2012 is a good year to which to convert all of the dates; since it is a leap year, any February 29ths in your data set will be handled smoothly.
I have something similarly ugly as Tim:
R> toSeason <- function(dat) { + + stopifnot(class(dat) == "Date") + + scalarCheck <- function(dat) { + m <- as.POSIXlt(dat)$mon + 1 # correct for 0:11 range + d <- as.POSIXlt(dat)$mday # correct for 0:11 range + if ((m == 3 & d >= 21) | (m == 4) | (m == 5) | (m == 6 & d < 21)) { + r <- 1 + } else if ((m == 6 & d >= 21) | (m == 7) | (m == 8) | (m == 9 & d < 21)) { + r <- 2 + } else if ((m == 9 & d >= 21) | (m == 10) | (m == 11) | (m == 12 & d < 21)) { + r <- 3 + } else { + r <- 4 + } + r + } + + res <- sapply(dat, scalarCheck) + res <- ordered(res, labels=c("Spring", "Summer", "Fall", "Winter")) + invisible(res) + } R>
And here is a test:
R> date <- Sys.Date() + (0:11)*30 R> DF <- data.frame(Date=date, Season=toSeason(date)) R> DF Date Season 1 2012-02-29 Winter 2 2012-03-30 Spring 3 2012-04-29 Spring 4 2012-05-29 Spring 5 2012-06-28 Summer 6 2012-07-28 Summer 7 2012-08-27 Summer 8 2012-09-26 Fall 9 2012-10-26 Fall 10 2012-11-25 Fall 11 2012-12-25 Winter 12 2013-01-24 Winter R> summary(DF) Date Season Min. :2012-02-29 Spring:3 1st Qu.:2012-05-21 Summer:3 Median :2012-08-12 Fall :3 Mean :2012-08-12 Winter:3 3rd Qu.:2012-11-02 Max. :2013-01-24 R>
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