Generate Code for Data Visualizations

Generate starter code in [Language/Library, e.g., 'Python using Matplotlib/Seaborn', 'R using ggplot2'] to create a '[Specific Chart Type, e.g., 'grouped bar chart', 'scatter plot with regression line', 'heatmap', 'density plot']'. 
Assume the data is in a dataframe 'df'.
The key variables are:
- X-axis: [Column name for x-axis]
- Y-axis: [Column name for y-axis]
- Grouping variable (if applicable): [Column name for color/hue/facet]
- Size/Value variable (if applicable): [Column name for bubble size/heatmap value]
Include basic customization like adding titles and axis labels.