Methods to Select the Scales and Starting Values for Axes in Linear Graphs

Graphs are an important component in physics laboratory reports. We have noticed that our students have difficulty selecting the scale and the starting value for an axis while generating graphs on graph paper. Recommendations concerning convenient scales and starting values are found in textbooks, laboratory manuals, and papers. Methods to select the scale are found in web sources; however, they are inadequate, because as illustrated later in this paper, they are explained by means of particular numerical examples (instead of as a general formulation) or trial and error. In this paper, the existing methods to select the scale are reformulated and expanded in a general form involving equations and variables, but no trial and error. Methods to select the starting value of an axis are not documented. In this paper, a general method is presented to select the starting value.