We Commonly use Cartesian coordinate system[20] to
visualize the time-series data and in this case,the horizontal
axis is commonly used to represent the time and the
longitudinal axis is used to represent the data. Figure 1. shows
the visualization result of the daily concentration values of
pollutant NO2 from Jan.1st, 2002 to Dec. 31th, 2011of Jinan
City,a kind of the time-series data set . In Figure 1. (a), the
horizontal axis represents days from 2002 to 2011 and the
longitudinal axis represents NO2 concentration daily values. In
Figure 1. , the horizontal axis represents days of a whole days
of one year, the longitudinal axis represents the ten years NO2
concentration daily values. Here we only described the two
dimensional data