日期格式为:YYYYmmdd
library(plyr)
result <- ddply(data,.(month = substr(date,5,6)),summarize,ma = mean(a),
mb = mean(b),
mc = mean(c))
sma<-function(x,n){ #x是数组,求n项平均sapply(1:length(x),function(i){
if(i>=n) mean(x[(i-n+1):i])
else mean(x[1:i])
})
}
用的时候就直接
sma(x,3)就行了
产生100个均值为0标准差为1的正态分布随机数:rnorm(100, mean = 0, sd = 1) 指数分布数 dnorm(x, mean = 5, sd = 1, log = TRUE)