Tableau Course
Density Maps
A density map uses colour intensity to show where data points concentrate across a geographic area — the hotter the colour, the denser the cluster. It reveals patterns of concentration that individual point markers obscure when thousands of overlapping dots make a map unreadable.
Density Maps — Concentration, Not Magnitude
A symbol map places one circle per data point. When your dataset has 10,000 orders spread across a country, a symbol map becomes a solid mass of overlapping dots — the individual points are invisible and the geographic pattern is lost. A density map solves this by blending all nearby points into a smooth colour gradient. Areas where many points cluster together glow with a warm, intense colour. Areas with sparse points remain cool or transparent. The result is an instant visual answer to the question: where does this activity concentrate?
Density maps are ideal for large row-level datasets — individual customer orders, delivery locations, incident reports, ride-hailing pickups, or any data where each row represents a single geographic event and the total count runs into the thousands or millions.
Building a Density Map — Step by Step
Density Map — Labelled Mockup
Intensity and Radius Controls
The Density mark type exposes two controls inside the Color channel: Intensity and the colour palette itself. Intensity controls the radius of influence each point exerts — how far its colour bleeds outward into neighbouring areas. A high intensity setting produces broad, soft glowing regions. A low intensity setting produces tight, sharp hotspots. The right intensity depends entirely on your data density and the geographic zoom level of the map.
Filtering a Density Map
Density maps respond to filters exactly like any other chart. Adding a filter on Category to the Filters shelf lets you switch between viewing order density for Furniture, Technology, and Office Supplies independently — revealing whether different product categories attract customers in different geographic areas. Adding a filter on Order Date lets you animate the density pattern over time, watching concentration shift between seasons or years.
To create an animated density map, drag Order Date (discrete Year or Quarter) to the Pages shelf. Use the playback controls that appear to step through time periods automatically — the density map redraws for each period, creating a visual animation of geographic concentration over time.
Density Map vs Symbol Map — Choosing the Right Type
| Aspect | Density Map | Symbol Map |
|---|---|---|
| Best for | Large row-level datasets — thousands of individual points | Aggregated data — one circle per city, state, or category |
| Encodes | Point concentration — how many events occur near each location | Measure magnitude — Sales, Profit, Count per location |
| Exact values | No — colour gradient shows relative intensity only | Yes — circle size and tooltip show exact Measure values |
| Overlapping points | Handled automatically — overlap increases colour intensity | Overlap obscures individual circles — needs opacity reduction |
Density maps are the right tool the moment your symbol map becomes unreadable — and that usually happens around 500 to 1,000 overlapping points. In Superstore, the row-level order data at postal code level produces exactly this problem: thousands of postal codes stacked on top of each other in the Northeast corridor. Switching to Density mark type transforms that illegible mass into a clean heatmap showing exactly where Superstore's customer base concentrates. The Pages shelf animation is worth learning for any dataset with a time dimension — watching the density pattern shift quarter by quarter reveals seasonal geographic patterns that no static chart can show. Always set your background map to Dark when using a warm density palette. The contrast between the dark map and the glowing warm colours is not just aesthetic — it dramatically improves the readability of low-intensity areas that would disappear against a light background.
Practice Questions
1. A symbol map of 10,000 order locations is an unreadable mass of overlapping dots. What single mark type change converts it into a density map?
2. You want the density map to animate through each year automatically, showing how geographic concentration shifts over time. How do you set this up?
3. A density map zoomed into a city shows large glowing blobs that bleed into each other, making individual hotspots hard to distinguish. Which control should you adjust and in which direction?
Quiz
1. A dataset has 50,000 individual delivery location rows. A symbol map is unreadable due to overlapping. Which map type is the correct replacement?
2. A density map uses the warm Density palette (yellow → orange → red). Which background map style makes the density colours most readable?
3. A stakeholder asks for exact order counts at each location from a density map. Can a density map provide this directly?
Next up — Lesson 30: Geospatial analysis — using spatial joins, custom territories, and geographic calculations to answer location-based business questions.