5.2.3. 4 Graph of Two or More variables
If the unit of measurement is the same, we can represent two or more variables on the same graph. This facilitaties comparison. However, when the number of variables is very large (say, exceeding five or six) and they are all shown on the same graph, the chart becomes quite confusing because different lines may cut each other and make it difficult to understand the behaviour of the variables. Therefore, for the sake of clarity we should not represent more than 5 or 6 variables on the same graph. When two or more variables are shown on the same graph it is desirable to use thick, thin, broken, dotted lines, etc. to distinguish between the various variables.