Quantize, quantile and threshold on 365 days
Wednesday 1 January is day 0, so the first column is shifted by three days (k + 3) to line weeks up from Sunday.
Discrete scales return one of a few fixed answers, usually colours. Ordinal scales turn categories into colours. Quantize, quantile and threshold scales turn numbers into classes, and each draws the class borders in a different place, which changes what the chart says.
Change the code and press Run (Ctrl+Enter). Predict what will happen first, then break it on purpose and read what changes. Your edits are saved and match the lesson page.
Ready for more? This phase has 4 hands-on exercises with automatic checks.
Practice questions
Write the code in the editor, run it, then open the model answer to compare.
Write a function classOf(rides) that returns "quiet", "normal", "busy" or "peak" for the borders 1,500, 2,500 and 3,500, using a scale. What is classOf(2500)?
Using the daily rides from the second example (rides), print the 75th percentile (the top border of a four-class quantile scale) and the share of days with more than 3,000 rides.
Explain it without notes
How do quantize and quantile cut the same data differently?
Why must a threshold scale's range have one more entry than its domain?
What happens when an ordinal scale meets a name it does not know, and how do you control it?
Preview
Console
Nothing logged yet.Expected console output
quantize borders: [ 1424.3, 2409.5, 3394.8 ]
quantile borders: [ 1702, 2484, 3365 ]
days per class, quantize: 34 / 142 / 100 / 89
days per class, quantile: 91 / 91 / 91 / 92
days per class, threshold: 49 / 134 / 105 / 77
1,499 -> 0 1,500 -> 1 NaN -> undefined too few colours: b
invertExtent of the third class: [ 2409.5, 3394.8 ]
with one 90,000 day, quantize: 0:100 3:1
with one 90,000 day, quantile: 0:25 1:25 2:25 3:26