✨ (line chart) set y-axis min default to 0

[sophiamersmann]

Resolves #3797

Summary

Makes 0 the new default minimum value for the y-axis of line charts

Details

About the default Grapher config

• With these changes, the default of yAxis.min depends on the chart type (0 for line charts, auto for others). As a result, yAxis.min can't be included in the default base layer (since there isn't a single default value that should apply to all configs)
• I removed the default value for both the x-axis and the y-axis because I want to keep using one definition for the axis. I haven't found a way to compose the JSON schema such that I can keep the axis definition in one place and change the default min value of y-axis only
• Since we changed the default grapher config, we have to re-compute the full configs of all charts

About the Grapher/config interface

• The auto value parsed from the config used to be translated to undefined for Grapher, which told Grapher to infer the min/max value from the data
• With these changes, the auto value is translated to Infinity, which also means "infer from data", and having no value triggers the default behaviour, which is usually "auto" behaviour but is overwritten to be 0 for line charts

About the admin

• The admin doesn't say 0 for line charts if the default behaviour is used because the value is actually undefined/Infinity

SVG tester

The SVG tester updates are technically correct. I'll re-export configs for the SVG tester next week after removing the default config layer.

To do

• Update explorers
  • climate-change
  • population-and-demography: chore: set yAxisMin to auto where missing owid-content#68

[sophiamersmann]

• ✨ (grapher) support multiple chart types / TAS-694 #4140
• 🔨 use fixed defaultGrapherConfig in migrations #4113
• 🔨 (grapher) turn related questions into an object / TAS-676 #4108
• 🔨 remove default layer from chart configs / TAS-675 #4103
• ✨ (line chart) set y-axis min default to 0 #4080 👈 (View in Graphite)
• 🐛 (explorer) merge configs correctly #4091
• ✨ log explorer views to google analytics #4098
• ✨ log grapher views to google analytics #4076
• master

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[owidbot]

Quick links (staging server):

Site	Admin	Wizard	Docs

Login: ssh owid@staging-site-line-chart-yaxis-min-viz

• Site-screenshots: https://github.com/owid/site-screenshots/compare/line-chart-yaxis-min-viz
• SVG tester: https://github.com/owid/owid-grapher-svgs/compare/line-chart-yaxis-min-viz

SVG tester:

Number of differences (default views): 31 (25d0a4) ❌
Number of differences (all views): 0 ✅

Edited: 2024-11-06 16:05:32 UTC
Execution time: 1.20 seconds

[marcelgerber]

Nice!

One thing I didn't entirely find out, but I think I got a sense: Existing charts stay unchanged in this, right? I.e., the migration makes it so the "effective chart diff" is empty?

[marcelgerber]

If I understand this correctly, then this is the default config before this PR was merged, right?

If that's the case, then let's make this more explicit - either in the name or in a comment.

[sophiamersmann]

Oh shoot, I copy-pasted the wrong config! This should just be the default config as it exists on this branch. I copied it over (instead of importing) because I realised that relying on the default config version of the code that is running the migration is a bit dangerous (because we really do need this specific version of the default config). Sorry for the confusion!

So, the default config we're working with doesn't have a default value for yAxis.min. Then, the gist of the migration is:

• If a chart relied on the default for yAxis.min being auto, add yAxis.min=auto to its patch config to make this explicit
• Then recompute the full config using the new default config
• The full config should thus be unchanged (but the patch config of a chart might have been changed)

Before reading your comment, I was testing an upstream PR upstream and I couldn't make sense of some of the chart diffs I was seeing. I'm pretty sure this is the reason – so thanks for spotting it! It probably would have taken ages to figure it out 🫠