Please read the image I have attached and convert it into runnable R code that reproduces this figure. Specific requirements are as follows:
1. **Image Parsing**: First briefly list the components identified in the image (such as data types, axes, layers, color mappings, annotations, etc., no more than 10 items), and only write the code after confirming them.
2. **Complete Reproduction**: The figure generated by the code must fully reproduce all elements, structure, and style of the original image, without omissions or fabrications; if there are multiple subplots, arrange them as panels a, b, c.
3. **Code Standards**: Write in R (prefer ggplot2, using patchwork or cowplot for panel assembly when necessary); the code should have clear structure and necessary comments, with data constructed via in-code simulation or built-in datasets, ensuring it can directly run and produce the figure.
4. **Layout Style**: Conform to academic paper figure standards, with consistent sans-serif fonts, line widths, and color schemes; axes, legends, titles, and labels should be complete and consistent with the original image.
5. **Output Format**: First provide the complete runnable R code, then attach a brief description of the code structure; please check yourself that the code syntax is correct with no undefined variables, ensuring it directly generates the target figure when run.
