Royal Greenwich Observatory sunspot areas by solar latitude, 1874–2013
A second tufte-viz demonstration. Same data, two treatments — but here the contrast is more severe because the default approach destroys the dataset's signature pattern.
Pre — typical default chart
The default move when handed sunspot-area-vs-latitude data: aggregate the 50 latitude bins into 5 broad bands and plot as time series. You can see the ~11-year cycle, but the latitude story — sunspots starting at high latitudes and migrating toward the equator within each cycle — is gone. Bands at ±30°N and ±15° both light up; you cannot tell that they do so sequentially within a single cycle. ~93,000 data cells reduced to 5 lines.
Post — Maunder butterfly diagram
The same data rendered as a 2D heatmap: every darker pixel marks a Carrington rotation × latitude bin where sunspots appeared, intensity proportional to area. Each "wing" is one ~11-year solar cycle. The migration is unmistakable: every cycle starts at high latitudes (±25–30°) and drifts toward the equator over ~11 years. Cycle 19 (mid-1950s) is the strongest on record; cycles 23 and 24 (2000s) are visibly weaker — a fact invisible in the line chart.
This redesign is the original Maunder butterfly diagram (E. Walter Maunder, 1904). It was Tufte-grade before Tufte. The point of the pre/post: a competent default approach can throw away the most important pattern in the data, and you'd never know unless you started with "what does the data look like in its highest-resolution form?"
What the skill changed
Aggregation → density. Default reduced 93k cells to 5 lines; Tufte-style preserves the full grid. Data density is itself a quality signal.
Color encoding → intensity encoding. Five rainbow lines → single monochrome intensity scale. Color now means one thing (more spots) instead of five (which band).
Time-as-x, value-as-y → time-as-x, position-as-y, value-as-intensity. Adding a dimension lets the spatial story emerge.
Cropped to the data's natural extent. Latitude axis goes to ±46° because that's where sunspots live; the polar zones are visually empty and were excluded. Range-frame thinking applied to a 2D grid.
Direct annotation. Solar cycle numbers labeled directly above each wing. No legend.