1. Concise and Clear: Avoid jargon and overly technical language. Use simple, direct language that's easily understood by your target audience.
2. Self-Contained: The legend should explain everything necessary to understand the figure, including:
* What is shown: Briefly describe the content of the figure (e.g., "Graph showing the relationship between...", "Microscopic image of...", "Map depicting the distribution of...").
* Key elements: Identify all key components, symbols, lines, bars, etc., and explain their meaning. Use a consistent legend within the figure itself, and refer to it in the written legend. (e.g., "Squares represent control group, circles represent treatment group"). If symbols or colors are used, explicitly state what they represent.
* Units and scales: Clearly state the units of measurement used for all axes, values, and other quantitative data. Indicate the scale (e.g., "Data are expressed as mean ± standard deviation," "Scale bar represents 10 μm").
* Statistical information (if applicable): If the figure includes statistical analyses, state the type of test used (e.g., "t-test," "ANOVA"), the p-value (e.g., "p < 0.05"), and the number of samples (n). Avoid excessive detail; keep it concise and relevant.
* Sample size (n): Always include the sample size for each group or condition represented.
* Abbreviations: Define any abbreviations used within the legend. If abbreviations are already defined in the main text, you may not need to redefine them here, but consistency is key.
3. Structure: While there is no rigid format, a generally effective structure is:
* A brief, descriptive title: This should clearly and concisely summarise the figure's content. It often answers the "what" question.
* Detailed description: This section elaborates on the content, including all the details mentioned above (key elements, units, scales, statistical analysis).
4. Example:
Poor Legend:
> Figure 1. Data.
Good Legend:
> Figure 1. Effect of different treatments on plant growth. Plant height (cm) was measured after 4 weeks of treatment with various concentrations of fertilizer (A, B, C). Data are presented as mean ± standard error of the mean (SEM) (n=10 per treatment). Statistical significance was determined using one-way ANOVA, *p < 0.05, **p < 0.01. Squares represent treatment A, circles represent treatment B, triangles represent treatment C.
5. Consider your audience: Tailor your legend to the level of expertise of your readers. A highly specialized journal may allow for more concise legends assuming a certain level of background knowledge, while a more general audience will require more explanation.
6. Review and revise: After writing your legends, review them carefully to ensure clarity, accuracy, and completeness. Have a colleague check them for any ambiguities.
By following these guidelines, you can create effective figure legends that enhance the clarity and impact of your research paper. Remember, a good figure legend should make your figures understandable and easily interpretable, even without reading the surrounding text.