Principles of Graph Plotting: Plotting a graph is also an art like preparing a table, which needs skill and experience. Some of the general principles can be stated as below.
As graphs are a visual interpretation of data, they can play tricks. If one data has been plotted with two different scales then they can create different impressions upon the reader’s mind. Therefore, scale manipulation can considerably alter the impact of a graph, which requires the necessity to see carefully that the graph does not distort the data and that it creates accurate and correct impressions.
As in the case of a table, a graph also must have a clear, short, and comprehensive title. It should have neither very long nor too short and it can explain the nature of data also.
Variables and Axis:
As we know there are two variables as independent variables and dependent variables. Variables that assign their value independently are known as independent variables. Variables that are dependent on their values on other variables are called dependent variables. The graph gives an easier way to find out the dependency of data. As a general rule, an independent variable should be placed on the horizontal (y-axis) axis and dependent variables are placed on the vertical (y-axis) axis. For example, time is an independent variable it should be placed always on the horizontal axis.
Further, it is necessary to carry correct impressions, the vertical scale does start from zero. If the highest value is so large then one can start scaling from zero and break in between where data has the least importance or is absent. For example, if the highest number is 1,000 and the lowest number is 600 then one can start scaling at zero on the vertical axis and make a break after 50 up to 500 and start again as 500, 550, 600, and so on up to 1,000.
More than one axes can be made in a vertical direction. If we want to make two axes then the first can be made on the left side and the second on the right side. For more than two axes we can change the different colors of the axes, scale, and curve.
Along each axis, we have to put axis titles with units, symbols, and scales. Graph title explaining the graph information should be given at the bottom of graph including graph number and type if any. Legends of the graph are also necessary to understand the multiple axes and curve on the graph.
There are many types of graphs in statistics such as histogram, frequency polygon, frequency curve, ogive or cumulative frequency curve are some of the examples. However, Microsoft excel gives a sufficiently large number of types including bar graphs, 3D graphs, pie graphs, line graphs, scattered graphs, and many others. Out of this graph, frequency curves are important for statistical analysis.
Make sure you also check our other amazing Article on : Presentation of Data