Draft Heart attack dataset
This scatterplot uses a heart disease dataset from Kaggle to explore the relationship between maximum heart rate achieved and resting electrocardiographic results, with age on the vertical axis. Each circle represents a patient, colored by gender. The visualization is built with React and D3 v5, using `scaleLinear`, `scaleOrdinal`, `extent`, and `format` from D3, with SVG rendering via custom `AxisBottom`, `AxisLeft`, and `Marks` components. Axes are drawn with D3’s tick generation, and hovering shows tooltips via SVG `<title>` elements.