利用时间序列数据进行探索性数据分析

data(AirPassengers)
class(AirPassengers)

1 ts

本着探索性数据分析（EDA）的精神，第一步是查看时间序列数据的图表：

plot(AirPassengers) # plot the raw data
abline(reg=lm(AirPassengers~time(AirPassengers))) # fit a trend line

对于进一步的 EDA，我们检查多年的周期：

cycle(AirPassengers)

     Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1949   1   2   3   4   5   6   7   8   9  10  11  12
1950   1   2   3   4   5   6   7   8   9  10  11  12
1951   1   2   3   4   5   6   7   8   9  10  11  12
1952   1   2   3   4   5   6   7   8   9  10  11  12
1953   1   2   3   4   5   6   7   8   9  10  11  12
1954   1   2   3   4   5   6   7   8   9  10  11  12
1955   1   2   3   4   5   6   7   8   9  10  11  12
1956   1   2   3   4   5   6   7   8   9  10  11  12
1957   1   2   3   4   5   6   7   8   9  10  11  12
1958   1   2   3   4   5   6   7   8   9  10  11  12
1959   1   2   3   4   5   6   7   8   9  10  11  12
1960   1   2   3   4   5   6   7   8   9  10  11  12

boxplot(AirPassengers~cycle(AirPassengers)) #Box plot across months to explore seasonal effects