Figures and tables
Your figures and tables, also known as display items, are essentially graphical representations of the results described in the text. They are also the most effective and efficient way to present your results. Good figures and tables quickly tell the reader exactly what you found in your study.
Researchers, journals editors and peer reviewers all appreciate being able to quickly understand your results. Therefore, it is worthwhile devoting some thought and attention to developing good quality figures and tables. Below are some ‘rules’ that should be followed when generating display items.
Display item guidelines
First, do not exceed the display item limits your target journal specifies. If you have more results than can be simply shown in the allowable number of display items, some (the least important) may need to be included in a Supplementary Information section, or described in the text with the statement “(data not shown).” You may need to consider an alternative journal if your first choice will not allow you to present all of your important data. However, if a journal allows more display items than is necessary to show your findings, do not add redundant or unnecessary display items simply because you can. All display items must have a clear and necessary purpose.
Second, data in figures and tables need to be easy to interpret. Data in a display item should be organized to convey the important message. Rather than combining multiple parameters or treatments into a single graphic, consider splitting the data across multiple simpler graphics that can be grouped together in a single figure. Clearly label graph axes, table columns and rows, and components of diagrams. Trend lines, scale bars and the results of any statistical tests should be shown, for example, by using an asterisk to indicate significance, or a variety of symbols to indicate different levels of significance. With large samples, report the % change or % difference as well as absolute values.
Third, legends accompanying display items need to stand alone so the display items are entirely understandable without needing to read the manuscript. Abbreviations, if used, should be defined, and technical terms should be avoided. What was done and what resulted should be clear. Statistical tests should be briefly described in the legends, with p values given and any symbols used defined. Legends, including their headings, should be written in the present tense with the exception of any methods described within them.
For example, use “Western blot showing an increase in the levels of p53 after…” rather than “Western blotting showed that the levels of p53 increased after…”. A general guideline to correct tense use in display items is: if a reader can see something in a display item, write about it in the present tense. If the reader cannot see something in the display item, but it was done to achieve what is seen in the display item, then write about it in the past tense.
Finally, avoid redundancies between the display items and the text. Do not create a display item to show information that can easily and briefly be stated in the text. Also, do not duplicate information among tables and figures. For example, do not make a table that shows the same information already in a figure. Importantly, do not embed figures and their legends within the text of the manuscript you plan to submit. Journal publishers usually require authors to send a separate file containing the display items, and another with the main manuscript text that includes figure and table legends listed at the end (usually following the references). Check your target journal’s instructions for authors for specific requirements.
If you prepare good quality, clear display items before writing the results section, it becomes much easier to write this section. Display items can be grouped in a logical order that progresses your argument and strengthens your hypothesis. With one subsection and one display item for each of your major findings, the subsection headings will be similar to the relevant legend headings. Also, the text in each subsection will provide a brief description of the findings shown in each display item, complete with the results of statistical analyses. Readers can be referred to the display items for more detail.
Tables are the best way to present large amounts of data with minimal description. The table shown above is a truncated version of a table in a paper published in The Journal of Clinical Investigation (doi:10.1172/JCI37622; reproduced with permission). The data presented clearly and economically in this table would have required a lot of word space if described in the text. All that was required to describe this table in the main text was: “Clinical characteristics of all patients and tumor samples are summarized in Table 1.” The figure below, taken from the same paper, contains many of the elements of a successful display item described here and listed in the checklist below.
- ‘Stand alone’ legends
- Comply with the journal's specified number of display items
- Avoid redundancy among display items or between display items and text
- Divide data showing different effects or parameters among different panels within the same display item
- Use scale bars, trend lines and clear labels, and show the results of statistical tests
- Avoid or define all symbols and abbreviations
- With large samples, show % changes/differences as well as absolute values
- Submit figures in a separate file or at the end of the manuscript file rather than embedded in the main text
- Check the instructions for authors for any specific requirements regarding format, size, color, number of items and any other parameters