the histogram

Bars touch because they are slices of one scale, not separate categories. Read the shape.

What it leaves outThe bin width is a decision, not a fact. Widen the bins and two humps become one; narrow them and noise starts to look like structure.

2 · intermediate · cartesian · rung 2 · what’s reported

shipped on the platform · hist

Three worked examples

What does a normal day look like?

Before you lookSketch, in the air or on paper, the shape you expect: a hump in the middle, a slope, or something else.

civichist_la_311_per_day.csv · 365 rows · 2 columns

the same 365 daily request counts, this time binned

What to look atThe bars touch, because they are slices of one number line. Change the bin count and watch the shape move — same data, different picture.

This example draws itself with a small script. With scripting off you can still read every word on this page, and the file itself is at data/hist_la_311_per_day.csv.

earth and spacehist_quake_magnitudes.csv · 2,508 rows · 1 columns · showing 400 of 2,508 rows on this page; the file has all of them

2,508 earthquake magnitudes

What to look atA long tail to the right. Set the bins to 8, then to 40, and decide which one you would put in front of a class.

This example draws itself with a small script. With scripting off you can still read every word on this page, and the file itself is at data/hist_quake_magnitudes.csv.

teen healthteen_estimate_precision.csv · 1,629 rows · 6 columns

how precisely each published teen-health number is actually known

What to look atEvery one of these 1,629 numbers came with a range around it, and this is how wide those ranges are. The middle one is about ten percentage points wide. Before you say one group is higher than another, find both ranges and check the gap is bigger than either of them.

This example draws itself with a small script. With scripting off you can still read every word on this page, and the file itself is at data/teen_estimate_precision.csv.

the pool

Now build one yourself.

The pool opens with this file and this shape already drawn, so your first move is to change something rather than to start from nothing. Bring your own CSV if you have one. Nothing is uploaded anywhere — the chart is drawn in your browser, your work saves there, and it downloads as a picture or as a project file you can open again.

Open the pool → the histogram · hist_la_311_per_day.csv