Graphs of Time Series
A time series is a sequence of values corresponding to successive points of time. Time series are graphed with time on the x axis and the other variable under consideration on the y axis. Such a graph is called historigram graphs of time series can be made in two types of scales.
a. Natural scale or
b.Ration scale
With natural scale there are two types or graphs:
Absolute historigram here we use original values
Index historigram here we use index number or relative values.
Sometimes false base line in the vertical scale is used where the portion of the scale which lies between zero and the smallest values of the variable is omitted .
To draw an absolute historigram take time (year months etc.)along x axis and original values along y axis. Plot the point and join them by straight lines.
If more than one time series pertaining to the related phenomena and belongs to the same period are to be shown on a graph then the scale on y axis is kept the same. The curves of for each time series are shown by different types of lines. However if two time series are expressed in two different units then we will have two scales one on the left and the other on the right.