Course notes

Gist 4063106

This example visualizes the density distribution of bicycle data from the `table_2007_2009_bicy` dataset, dividing points into five quantile-based buckets. It shows how the maximum point count and density vary across these buckets, revealing spatial clustering patterns. The SQL code uses CartoDB functions such as `st_snaptogrid` and `CDB_XYZ_Resolution` to aggregate points into grid cells at a given zoom level, then calculates density per cell and assigns quartiles via `ntile(5)`. The final output summarizes each bucket’s maximum values, providing a statistical overview of the underlying geographic data.

Aandrewxhill

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Fork of Fork of Fork of Grid Sampling on Census Tracts - Coloring by Data

This visualization displays New York City census tracts as a grid of colored squares, where each square’s color intensity represents the Black population count within the tract containing that grid point. The map supports drag-to-pan and zoom interactions, using a geographic orthographic projection. It relies on D3’s `geoOrthographic` and `geoPath`, alongside Turf’s `booleanPointInPolygon` and an RBush spatial index for efficient point-in-polygon queries. Data comes from the 2023 Census Bureau shapefiles and American Community Survey demographics, both loaded as JSON.

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Census Tracts Contours with City Labels

This interactive visualization displays demographic data across New York City census tracts using colored contour layers, with orange representing the Black population and green representing the white population, overlaid with city labels. The code builds a spatial index with RBush, samples data points through turf.booleanPointInPolygon, and uses d3.contours with blur2 smoothing to generate the density regions. Orthographic projection, panning, and zooming are implemented via d3.geoPath, drag, and zoom behaviors. Census tract boundaries and demographic data come from processed government shapefiles and ACS datasets.

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New York Census Tracts

A choropleth-style map of New York census tracts renders all tract polygons in gray, with tract borders drawn in dark gray to reveal the state's internal administrative divisions. The visualization loads pre-projected TopoJSON geographic data (`ny.json`), which the code trims by excluding water-only county rows. Using d3.geo.path with a null projection for rendering and topojson.feature to convert the geometry, the map displays tract IDs as SVG title tooltips on hover. The style uses default light gray fills for each tract polygon.

Fork of Grid Sampling on Census Tracts - Optimized

This example visualizes New York City census tracts on an orthographic globe projection, styled as a choropleth-like grid of points sampling each tract’s interior. The visualization shows demographic data from the U.S. Census Bureau’s 2023 ACS estimates. It uses `geoOrthographic`, `geoPath`, and a custom `map` module to render tract boundaries and a uniform grid of points, with an RBush spatial index and turf’s `booleanPointInPolygon` to test which grid points fall inside tracts. Drag and zoom interactions adjust the globe’s rotation and scale via `d3.drag` and `d3.zoom`.

Gist 1198897

This visualization demonstrates the geographic distribution of the 2010 U.S. Census data, mapping population counts and related demographic metrics across states. Built with Ruby and CartoDB importer, it renders interactive choropleth maps using color-coded polygons to represent data values, allowing users to explore spatial patterns in the dataset. The visualization leverages Google Spreadsheet integration for data input and PostgreSQL for storage, with map rendering handled through CartoDB’s geospatial processing pipeline.

Aandrewxhill

Fork of Fork of Grid Sampling on Census Tracts - Coloring the Grid

This interactive map visualizes New York census tracts on an orthographic projection, with a uniform grid of circles overlaid across the viewport. Grid points inside tract boundaries render as larger, colored circles using a sequential Cubehelix color scale, while points outside remain small. The code uses `d3.geoOrthographic`, `d3.geoPath`, and `topojson-client` for rendering, with `@turf/turf` for point-in-polygon tests and `rbush` for spatial indexing. Census data comes from a Gist, and drag and zoom interactions adjust rotation and scale.

Fork of Grid Sampling on Census Tracts - Contours from Points

This interactive map visualizes contours of Black population density across New York City census tracts, projected on a rotatable orthographic globe. The visualization uses D3’s `geoOrthographic`, `geoPath`, and `contourDensity` APIs to generate smoothed density bands from tract centroid points weighted by population and land area, colored with a sequential orange scale. Census tract boundaries appear as thin black outlines, while drag and zoom interactions rotate and scale the projection in real time via `d3.drag` and `d3.zoom`. Data comes from the 2023 Census shapefiles and ACS demographics, loaded via `d3.json` and processed with `topojson-client`.