Reference / Charts

The question picks the chart.

Not the other way around. Each of these is a question a dataset can answer, the form that answers it, and the specific ways that form goes on to mislead people.

Questions: 6
Chart forms: 12
Each with: how it misleads

Chart

Showing how something moved over time.

The most-used chart form and the one with the most implied claims. A line says the values between the points would have been on the line.

Line chart · Time series

Chart

Comparing categories against each other.

The workhorse. Length along a common baseline is the most accurately compared encoding available, and the rules that protect it are strict for that reason.

Bar chart · Column chart · Grouped bars

Chart

Showing the spread rather than the average.

The chart that shows whether the average you have been quoting describes anyone at all.

Histogram

Chart

Showing whether two things move together.

The only common chart form whose main risk is what the reader concludes rather than what the chart shows.

Scatter plot

Chart

Showing what a total is made of.

Correct when the reader's question is genuinely about shares of one total, and wrong more often than it is used.

Stacked bar · 100% stacked bar

Chart

Showing how one total became another.

The form for a question no other chart answers: not what changed, but what the change was made of.

Waterfall chart · Bridge chart · Margin bridge

What it will not draw

Refused at the schema layer, which is why no chart in this product has ever been one.

The agent emits an intent from the closed list above, and one compiler renders it. These forms have no intent to emit.

3D anything: Perspective makes two equal values look different. There is no case where the third dimension carries data.
Gauges and speedometers: An enormous amount of ink for one number, and the dial implies a range that is usually invented.
Radar charts: Area scales with the square of the values and the shape changes entirely if you reorder the axes.
Word clouds: Size encodes frequency, which is the least interesting thing about a word, and nothing is comparable.
Pie charts: Angles are hard to compare at any number of slices, and past a few of them the labels leave the chart anyway. Composition compiles to a stacked bar instead.
Per-series arbitrary colour: Colour means something specific in this product. A series that picks its own hue breaks the meaning everywhere else.