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fix(sql): correct symlog scale invert to be the inverse of apply #1059

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fix(sql): correct symlog scale invert to be the inverse of apply #1059

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2 changes: 1 addition & 1 deletion packages/mosaic/sql/src/transforms/scales.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -88,7 +88,7 @@ function scaleSymlog({ constant = 1 } = {}): ScaleTransform<number> {
const _ = +constant;
return {
apply: x => Math.sign(x) * Math.log1p(Math.abs(x)),
invert: x => Math.sign(x) * Math.exp(Math.abs(x) - _),
invert: x => Math.sign(x) * (Math.exp(Math.abs(x)) - _),
sqlApply: c => (c = asNode(c), mul(sign(c), ln(add(_, abs(c))))),
sqlInvert: c => mul(sign(c), sub(exp(abs(c)), _))

@domoritz domoritz Jun 26, 2026

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Can we test that the sql and js versions are consistent?

};
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11 changes: 11 additions & 0 deletions packages/mosaic/sql/test/scales.test.ts
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@@ -0,0 +1,11 @@
import { expect, describe, it } from 'vitest';
import { scaleTransform } from '../src/index.js';

describe('scaleTransform', () => {
it('symlog invert is the inverse of apply', () => {
const s = scaleTransform<number>({ type: 'symlog' });

@domoritz domoritz Jun 26, 2026

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Should we test this across constants?

for (const x of [5, 10, 100, -7, 1, 0.5]) {
expect(s.invert(s.apply(x))).toBeCloseTo(x, 9);
}
});
});