In this blog post graphic methods are used to describe Serbian quarterly transportation time series.
Two types of a line graph could be used to show changes in quarterly transportation over time. The first displays both time series on a single graph. This graph won’t be used because of the different measurement units. The first series is measured in passenger km and the second series in ton km. The second type of graph displays each series on a separate panel. On such graph any persistent pattern related to trend or seasonal factors should be clearly visible.
Figure 1 shows line graphs of quarterly transportation time series on the separate panels.
From Figure 1 is quite clear that the Value of services in road passenger transport series fluctuate around some constant level. The Value of services in road freight transport series shows an increasing trend with small variation around such trend.
From these plots it is difficult to make any comment on the seasonal patterns in two series. Therefore these two series will be further examined on the seasonal plots.