r - 如何计算月均值？

Question

我有这样的每日天气预报。我想要的是计算最高、最低和观测温度的月平均值，然后绘制这三条线。我已经像这样转换日期格式：

Date = as.POSIXlt(Weather2011$Date, format = "%m/%d/%Y")  
Year = as.numeric(format(Date, format = "%Y"))
Month = as.numeric(format(Date, format = "%m"))
Week = as.numeric(format(Date, format = "%U"))
Weekday = as.numeric(format(Date, format = "%w"))

Weather2011看起来像这样：

Date      Max.Temp  Min.Temp  Temp  Date        Year   Month  Week  Weekday
6/3/2010  87        63        63    2010-06-03  2010   6      22    4
6/4/2010  83        63        73    2010-06-04  2010   6      22    5

Answer 1

我发现 tapply 效果很好。前任。

x <- seq(from=as.Date("2000-01-01"), to=as.Date("2004-12-31"), by="day")
y <- sin(seq(from=0, to=2*pi*5,length.out=length(x)))+rnorm(length(x))
yyyymm <- paste(format(as.POSIXlt(x), format="%Y-%m"), "01", sep="-")
MEAN <- tapply(y, yyyymm, mean)
MAX <- tapply(y, yyyymm, max)
MIN <- tapply(y, yyyymm, min)
#plots
x11()
par(mfcol=c(1,2))
plot(x,y, ylim=range(MEAN, MAX, MIN), ylab="", xlab="")
plot(as.POSIXlt(names(MEAN)), MEAN, t="l", ylim=range(MEAN, MAX, MIN), ylab="", xlab="")
lines(as.POSIXlt(names(MEAN)), MAX, lty=2)
lines(as.POSIXlt(names(MEAN)), MIN, lty=2)