Polyarea Chart by Alex Katona
A common business question is "How does the percent of total for a category change over time?" Some ways that are typically used to visualize this data include a stacked area chart, stacked bar chart, or line chart with a line for each category. However, there are disadvantages to using these approaches. In a stacked area chart and stacked bar chart, the changing position of the upper and lower bounds make it difficult to determine if the percent of total increases or decreases over time for categories in the middle. Using a line chart with a line for each category, the lines may overlap and result in overcrowding of categories that have a similar percent of total. To solve for these issues, I created a new chart type using D3.js that combines many area charts, hence the name Polyarea chart.