让我有以下数据:对于每小时数据,获得最大的价值每天
time <- seq(ISOdate(2007,7,1,0), ISOdate(2008,4,5,23), by = "1 hour")
y <- rnorm(n = length(time))
year <- as.numeric(substr((as.character(time)), 1, 4)) # year number as numeric
month <- as.numeric(substr((as.character(time)), 6, 7)) # month number as numeric
day <- as.numeric(substr((as.character(time)), 9, 10)) # day number as numeric
hour <- as.numeric(substr((as.character(time)), 12, 13)) # hour number as numeric
dat <- data.frame(year=year, month=month, day=day, hour=hour, y = y)
每一天,有在每个小时(0〜23)24个y
值。现在我必须每天最多找到y
。也就是说,对于“2007-10-05”日期,在每个小时(0到23)中获得的值有24 y
,我必须获得“2007-10-05”日的最大值。因此,从“2007-07-01”到“2008-04-05”之间有279天,因此我将获得279个最大值y
值。
我该怎么做?