fix(axes): format tick labels correctly for small numbers in exponential notation - #7768
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Pull request overview
Fixes tick label formatting in numFormat for very small numbers where String(v) returns exponential notation, preventing invalid/truncated tick strings.
Changes:
- Detects exponential notation from String(v) and splits mantissa/exponent before applying rounding/truncation.
- Re-attaches the exponent after formatting the mantissa to avoid slicing into the exponent.
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| var adjustedTickRound = tickRound + exponentVal; | ||
| if(dp) { | ||
| if(adjustedTickRound < 0) { | ||
| mantissa = mantissa.slice(0, dp - 1); | ||
| } else { | ||
| mantissa = mantissa.slice(0, dp + adjustedTickRound).replace(/\.?0+$/, ''); | ||
| } |
| } else { | ||
| mantissa = mantissa.slice(0, dp + adjustedTickRound).replace(/\.?0+$/, ''); | ||
| } | ||
| } |
| var vStr = String(v); | ||
| var ep = vStr.indexOf('e'); | ||
| if(ep >= 0) { | ||
| var mantissa = vStr.slice(0, ep); | ||
| var exponentStr = vStr.slice(ep); | ||
| var dp = mantissa.indexOf('.') + 1; | ||
| var exponentVal = parseInt(exponentStr.slice(1), 10); | ||
| var adjustedTickRound = tickRound + exponentVal; | ||
| if(dp) { | ||
| if(adjustedTickRound < 0) { | ||
| mantissa = mantissa.slice(0, dp - 1); | ||
| } else { | ||
| mantissa = mantissa.slice(0, dp + adjustedTickRound).replace(/\.?0+$/, ''); | ||
| } | ||
| } | ||
| v = mantissa + exponentStr; | ||
| } else { | ||
| v = vStr; | ||
| var dp = v.indexOf('.') + 1; | ||
| if(dp) v = v.slice(0, dp + tickRound).replace(/\.?0+$/, ''); | ||
| } |
| v = String(v); | ||
| var dp = v.indexOf('.') + 1; | ||
| if(dp) v = v.slice(0, dp + tickRound).replace(/\.?0+$/, ''); | ||
| var vStr = String(v); | ||
| var ep = vStr.indexOf('e'); | ||
| if(ep >= 0) { | ||
| var mantissa = vStr.slice(0, ep); | ||
| var exponentStr = vStr.slice(ep); | ||
| var dp = mantissa.indexOf('.') + 1; | ||
| var exponentVal = parseInt(exponentStr.slice(1), 10); | ||
| var adjustedTickRound = tickRound + exponentVal; | ||
| if(dp) { | ||
| if(adjustedTickRound < 0) { | ||
| mantissa = mantissa.slice(0, dp - 1); | ||
| } else { | ||
| mantissa = mantissa.slice(0, dp + adjustedTickRound).replace(/\.?0+$/, ''); | ||
| } | ||
| } | ||
| v = mantissa + exponentStr; | ||
| } else { | ||
| v = vStr; | ||
| var dp = v.indexOf('.') + 1; | ||
| if(dp) v = v.slice(0, dp + tickRound).replace(/\.?0+$/, ''); | ||
| } |
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What do you think of replacing most of this with a call to toFixed? The exponent portion should get added further down on line 2240 (in your branch).
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@camdecoster Applied! Replaced the custom mantissa slicing with a clean oFixed call. |
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There was some funkiness with adding the rounding increment, so I made a few changes. Now the tests are passing! Speaking of which, could you please add some tests that check this new approach? Also, could you please add a draftlog? |
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…otation and add draftlog
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Hi @camdecoster, I've added the tests for this approach in numformat_test.js and added the draftlog as requested! All CI checks are passing successfully. Let me know if there's anything else needed. |
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Friendly nudge @camdecoster! As everything is fully updated and all CI checks are passing, could you please take another look and approve this so we can merge? Thank you! |
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I'm taking a look today. |
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camdecoster
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FYI, some of the obvious issues that this PR addresses are now managed by the changes in #7901. That being said, this change is still useful. Thanks for your contribution!
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What this PR does
This PR fixes a bug in src/plots/cartesian/axes.js where formatting very small numbers could result in invalid tick strings (e.g. "-9.381779999999999e-") when String(v) produces exponential notation but the numFormat logic slices the string indiscriminately.
Fix details
When exponential notation is present, the logic now separates the mantissa from the exponent, applies precision formatting to the mantissa, and re-attaches the exponent string, avoiding string truncation that removes the exponential component.
Tested against locally failing reproductions and verified using test-jasmine to ensure no existing suites are broken.