Guide to Graphing in Ecology Laboratory | BIO 41L, Papers of Ecology and Environment

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Appendix 5 - Guide to Graphing

The goal of a figure such as a line or bar graph is to summarize your data in an easily understandable, visually pleasing way. Your graph should be ‘self- contained’ so that anyone who reads it should be able to interpret it successfully, even if they are unfamiliar with the details of your research study. Listed below is the information needed for a complete graph (Note: you may sometimes need additional items, e.g., a legend if multiple colors or symbols are used).

1. Figure title
   • The title should be a concise description of the results in the figure.
   • Example: ‘The Effect of Different Soil Temperatures on Alfalfa Growth’
2. X-axis title
   • The independent variable should go on the x-axis.
   • Include measurement units if applicable (e.g., mm, kg, etc.)
   • Example: ‘Soil Temperature’
3. X-axis labels
   • Use names for categorical independent variables like soil type (e.g, sand, silt, clay), or discontinuous variables such as different experimental treatments. These will typically be displayed using a bar graph.
   • Use numbers (measurement scale) for continuous independent variables like time, distance, temperature, etc. (e.g., 10-25ºC). These will typically be used for a line graph. To decide how to number the lines on the axis: o Consider the number of lines available. Your figure should take up most of the space on the graph paper, so if you have a short range of numbers you may need to skip lines in between (e.g., 10. .11. .12. .13). If you have the opposite situation with more numbers than lines, you can count by multiples (e.g., 10, 15, 20…). Be sure you are consistent in your spacing so the scale is evenly distributed. o Consider the spacing of your data. For example, if your data range from 10-25ºC, you probably do not want to your axis labels to start from 0ºC or go all the way to 100ºC or you will have a lot of empty space in the graph. Keep in mind that your axis scale will affect how the data are perceived.
4. Y-axis title
   • The dependent variable should go on the y-axis.
   • Include measurement units if applicable (e.g., mm, kg, etc.) and note if the measurement is an average (mean, median, mode).

to show the most likely trend indicated by the location of the points. Figure 4 : Pie Graph

• Typically used to show percentages of a whole. Figure 5. Histogram (Frequency Distribution)
• Used to summarize data by showing the frequency (how many times) a particular interval of data was observed.