Data Dive · Rung 3 · What's Related · 3.4

Change the bin, move the cluster

Not one data point changes.

Runs in 20 minutes · everything you need is on this page · no network, no accounts, nothing for the students to open

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Two kilometre bins

Where the requests concentrate

The same 1,500 requests, binned at 2 kmhexagon centres - only the bin size changes between these twolatitudelongitudea hexagon holding requeststhe busiest bin1

1,500 LA 311 requests, hex-binned at 2 km. Busiest bin marked.

33.997 N
-118.433 W -- Westchester
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Five kilometre bins

The same 1,500 points

The same 1,500 requests, binned at 5 kmhexagon centres - only the bin size changes between these twolatitudelongitudea hexagon holding requeststhe busiest bin1

Same data. Only the bin size changed.

34.051 N
-118.283 W -- Echo Park
7 km
how far the answer moved
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The point

Nobody chose those hexagons for your question

Somebody chose them for the picture. This has a name — the modifiable areal unit problem — and it applies to every map drawn in zones: districts, precincts, ZIP codes, attendance areas.

The three questions
  1. What decided the boundaries on this map, and who decided it?
  2. Which map is right?
  3. You are about to tell somebody demand concentrates here. What must you publish alongside that sentence?
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After the dive

The shapes on this page, in the library’s own words

the hexagonal binning map

When there are too many dots to read, this counts them into tiles so you can see where they pile up.

What it leaves outChange the size of the tiles and the hot spot can move. Same data, different answer.
the dot density map

Where this is concentrated.

What it leaves outThe dots are scattered at random inside each area — they are not real addresses. A coarse dot-per-count can make a busy place look empty.

library · ladder · dives · the pool · this dive’s worksheet

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