fix(xy): non-stacked as percentage (#1504)

Backports the following commits to 38.0.x:
 - feat: expose computeRatioByGroups fn (#1495)

integration/tests/bar_stories.test.ts

@@ -223,4 +223,21 @@ describe('Bar series stories', () => {
       );
     });
   });
+  describe('Stacked bars configs', () => {
+    it('percentage stacked with internal fn', async () => {
+      await common.expectChartAtUrlToMatchScreenshot(
+        'http://localhost:9001/?path=/story/bar-chart--stacked-as-percentage&globals=theme:light&knob-mode=stackAsPercentage&knob-use computeRatioByGroups fn=',
+      );
+    });
+    it('percentage stacked with external fn', async () => {
+      await common.expectChartAtUrlToMatchScreenshot(
+        'http://localhost:9001/?path=/story/bar-chart--stacked-as-percentage&globals=theme:light&knob-mode=stackAsPercentage&knob-use computeRatioByGroups fn=true',
+      );
+    });
+    it('non stacked with external fn', async () => {
+      await common.expectChartAtUrlToMatchScreenshot(
+        'http://localhost:9001/?path=/story/bar-chart--stacked-as-percentage&globals=theme:light&knob-mode=unstacked&knob-use computeRatioByGroups fn=true',
+      );
+    });
+  });
 });

packages/charts/api/charts.api.md

@@ -476,6 +476,11 @@ export type ColorVariant = $Values<typeof ColorVariant>;
 // @public
 export type ComponentWithAnnotationDatum = ComponentType<LineAnnotationDatum>;
 
+// @public
+export function computeRatioByGroups<T extends Record<string, unknown>>(data: T[], groupAccessors: GroupKeysOrKeyFn<T>, valueAccessor: (k: T) => number | null | undefined, ratioKeyName: string): (T & {
+    [x: string]: number | null | undefined;
+})[];
+
 // @public (undocumented)
 export type ContinuousDomain = [min: number, max: number];
 
@@ -889,6 +894,9 @@ export type GroupByAccessor = (spec: Spec, datum: any) => string | number;
 // @public
 export type GroupByFormatter = (value: ReturnType<GroupByAccessor>) => string;
 
+// @public (undocumented)
+export type GroupByKeyFn<T> = (data: T) => string;
+
 // @alpha (undocumented)
 export type GroupByProps = Pick<GroupBySpec, 'id' | 'by' | 'sort' | 'format'>;
 
@@ -907,6 +915,9 @@ export interface GroupBySpec extends Spec {
 // @public (undocumented)
 export type GroupId = string;
 
+// @public (undocumented)
+export type GroupKeysOrKeyFn<T> = Array<keyof T> | GroupByKeyFn<T>;
+
 // @alpha (undocumented)
 export const Heatmap: React_2.FunctionComponent<Pick<HeatmapSpec, 'id' | 'data' | 'colorScale'> & Partial<Omit<HeatmapSpec, 'chartType' | 'specType' | 'id' | 'data'>>>;
 

packages/charts/src/chart_types/xy_chart/utils/group_data_series.ts

@@ -7,8 +7,12 @@
  */
 
 type Group<T> = Record<string, T[]>;
-type GroupByKeyFn<T> = (data: T) => string;
-type GroupKeysOrKeyFn<T> = Array<keyof T> | GroupByKeyFn<T>;
+
+/** @public */
+export type GroupByKeyFn<T> = (data: T) => string;
+
+/** @public */
+export type GroupKeysOrKeyFn<T> = Array<keyof T> | GroupByKeyFn<T>;
 
 /** @internal */
 export function groupBy<T>(data: T[], keysOrKeyFn: GroupKeysOrKeyFn<T>, asArray: false): Group<T>;

packages/charts/src/chart_types/xy_chart/utils/stacked_series_utils.ts

@@ -18,7 +18,7 @@ import {
 
 import { SeriesKey } from '../../../common/series_id';
 import { ScaleType } from '../../../scales/constants';
-import { clamp } from '../../../utils/common';
+import { clamp, isFiniteNumber } from '../../../utils/common';
 import { DataSeries, DataSeriesDatum } from './series';
 import { StackMode } from './specs';
 
@@ -59,6 +59,7 @@ export function formatStackedDataSeriesValues(
     acc[curr.key] = curr;
     return acc;
   }, {});
+  const stackAsPercentage = stackMode === StackMode.Percentage;
 
   const xValuesArray = [...xValues];
   const reorderedArray: Array<D3StackArrayElement> = [];
@@ -77,10 +78,13 @@ export function formatStackedDataSeriesValues(
         reorderedArray[xIndex] = { x };
       }
       // y0 can be considered as always present
-      reorderedArray[xIndex][`${key}-y0`] = y0;
+      reorderedArray[xIndex][`${key}-y0`] = isFiniteNumber(y0) ? (stackAsPercentage ? Math.abs(y0) : y0) : y0;
       // if y0 is available, we have to count y1 as the different of y1 and y0
       // to correctly stack them when stacking banded charts
-      reorderedArray[xIndex][`${key}-y1`] = (y1 ?? 0) - (y0 ?? 0);
+      const nonNullY1 = y1 ?? 0;
+      const nonNullY0 = y0 ?? 0;
+      reorderedArray[xIndex][`${key}-y1`] =
+        (stackAsPercentage ? Math.abs(nonNullY1) : nonNullY1) - (stackAsPercentage ? Math.abs(nonNullY0) : nonNullY0);
       dsMap.set(x, d);
     });
     xValueMap.set(key, dsMap);

packages/charts/src/index.ts

@@ -95,3 +95,7 @@ export { Pixels, Ratio } from './common/geometry';
 export { AdditiveNumber } from './utils/accessor';
 export { FontStyle, FONT_STYLES } from './common/text_utils';
 export { Color } from './common/colors';
+
+// data utils
+export { GroupKeysOrKeyFn, GroupByKeyFn } from './chart_types/xy_chart/utils/group_data_series';
+export { computeRatioByGroups } from './utils/data/data_processing';

packages/charts/src/utils/common.ts

@@ -617,3 +617,8 @@ const oppositeAlignmentMap: Record<string, HorizontalAlignment | VerticalAlignme
 export function getOppositeAlignment<A extends HorizontalAlignment | VerticalAlignment>(alignment: A): A {
   return (oppositeAlignmentMap[alignment] as A) ?? alignment;
 }
+
+/** @internal */
+export function isFiniteNumber(value: unknown): value is number {
+  return Number.isFinite(value);
+}

packages/charts/src/utils/data/data_processing.ts

@@ -0,0 +1,55 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { groupBy, GroupKeysOrKeyFn } from '../../chart_types/xy_chart/utils/group_data_series';
+import { isFiniteNumber } from '../common';
+
+/**
+ * The function computes the participation ratio of a value in the total sum of its membership group.
+ * It returns a shallow copy of the input array where each object is augmented with the computed ratio.
+ *
+ * @remarks
+ * The ratio is computed using absolute values.
+ * Product A made a profit of $200, and product B has a loss of $300. In total, the company lost $100 ($200 – $300).
+ * Product A has a weight of: abs(200) / ( abs(200) + abs(-300) ) * 100% = 40%
+ * Product B has a weight of: abs(-300) / ( abs(200) + abs(-300) ) * 100% = 60%
+ * Product A and product B have respectively a weight of 40% and 60% in the formation of the overall total loss of $100.
+ *
+ * We don't compute the ratio for non-finite values. In this case, we return the original non-finite value.
+ *
+ * If the sum of the group values is 0, each ratio is considered 0.
+ *
+ * @public
+ * @param data - an array of objects
+ * @param groupAccessors - an array of accessor keys or a fn to describe an unique id for each group
+ * @param valueAccessor - a fn that returns the value to use
+ * @param ratioKeyName - the object key used to store the computed ratio
+ */
+export function computeRatioByGroups<T extends Record<string, unknown>>(
+  data: T[],
+  groupAccessors: GroupKeysOrKeyFn<T>,
+  valueAccessor: (k: T) => number | null | undefined,
+  ratioKeyName: string,
+) {
+  return groupBy(data, groupAccessors, true)
+    .map((groupedData) => {
+      const groupSum = groupedData.reduce((sum, datum) => {
+        const value = valueAccessor(datum);
+        return sum + (isFiniteNumber(value) ? Math.abs(value) : 0);
+      }, 0);
+      return groupedData.map((datum) => {
+        const value = valueAccessor(datum);
+        return {
+          ...datum,
+          // if the value is null/undefined we don't compute the ratio, we just return the original null/undefined value
+          [ratioKeyName]: isFiniteNumber(value) ? (groupSum === 0 ? 0 : Math.abs(value) / groupSum) : value,
+        };
+      });
+    })
+    .flat();
+}

storybook/stories/bar/12_stacked_as_percentage.story.tsx

@@ -6,47 +6,82 @@
  * Side Public License, v 1.
  */
 
-import { boolean } from '@storybook/addon-knobs';
+import { boolean, select } from '@storybook/addon-knobs';
 import React from 'react';
 
-import { Axis, BarSeries, Chart, Position, ScaleType, Settings, StackMode } from '@elastic/charts';
+import {
+  Axis,
+  BarSeries,
+  Chart,
+  Position,
+  ScaleType,
+  Settings,
+  StackMode,
+  computeRatioByGroups,
+} from '@elastic/charts';
 
+import { AnnotationDomainType, LineAnnotation } from '../../../packages/charts/src/chart_types/specs';
 import { useBaseTheme } from '../../use_base_theme';
 
 export const Example = () => {
-  const stackMode = boolean('stacked as percentage', true) ? StackMode.Percentage : undefined;
+  const modes = select(
+    'mode',
+    { stack: 'stack', stackAsPercentage: 'stackAsPercentage', unstacked: 'unstacked' },
+    'stackAsPercentage',
+  );
+  const stack = modes !== 'unstacked' ? ['x'] : undefined;
+  const stackMode = modes === 'stackAsPercentage' ? StackMode.Percentage : undefined;
+
+  const originalData = [
+    { x: 'pos/neg', y: -10, g: 'a' },
+    { x: 'pos/neg', y: 10, g: 'b' },
+
+    { x: 'zero/zero', y: 0, g: 'a' },
+    { x: 'zero/zero', y: 0, g: 'b' },
+
+    { x: 'zero/pos', y: 0, g: 'a' },
+    { x: 'zero/pos', y: 10, g: 'b' },
+
+    { x: 'null/pos', y: null, g: 'a' },
+    { x: 'null/pos', y: 10, g: 'b' },
+
+    { x: 'pos/pos', y: 2, g: 'a' },
+    { x: 'pos/pos', y: 8, g: 'b' },
+
+    { x: 'neg/neg', y: -2, g: 'a' },
+    { x: 'neg/neg', y: -8, g: 'b' },
+  ];
+
+  const data = boolean('use computeRatioByGroups fn', false)
+    ? computeRatioByGroups(originalData, ['x'], (d) => d.y, 'y')
+    : originalData;
+
   return (
     <Chart>
-      <Settings showLegend showLegendExtra legendPosition={Position.Right} baseTheme={useBaseTheme()} />
-      <Axis id="bottom" position={Position.Bottom} title="Bottom axis" showOverlappingTicks />
+      <Settings baseTheme={useBaseTheme()} />
+      <Axis id="bottom" position={Position.Bottom} />
 
       <Axis
         id="left2"
-        title="Left axis"
         position={Position.Left}
-        tickFormat={(d: any) => (stackMode === StackMode.Percentage ? `${Number(d * 100).toFixed(0)} %` : d)}
+        showGridLines
+        ticks={5}
+        style={{ axisLine: { visible: false }, tickLine: { visible: false }, tickLabel: { padding: 5 } }}
+        gridLine={{ stroke: 'rgba(128,128,128,0.5)', strokeWidth: 0.5 }}
+        tickFormat={(d: any) => (modes === 'stackAsPercentage' ? `${Number(d * 100).toFixed(0)} %` : `${d}`)}
       />
-
       <BarSeries
         id="bars"
-        xScaleType={ScaleType.Linear}
+        xScaleType={ScaleType.Ordinal}
         yScaleType={ScaleType.Linear}
         xAccessor="x"
         yAccessors={['y']}
-        stackMode={stackMode}
-        stackAccessors={['x']}
+        stackAccessors={stack}
+        stackMode={stack && stackMode}
         splitSeriesAccessors={['g']}
-        data={[
-          { x: 0, y: 4, g: 'b' },
-          { x: 1, y: 5, g: 'b' },
-          { x: 2, y: 8, g: 'b' },
-          { x: 3, y: 2, g: 'b' },
-          { x: 0, y: 2, g: 'a' },
-          { x: 1, y: 2, g: 'a' },
-          { x: 2, y: 0, g: 'a' },
-          { x: 3, y: null, g: 'a' },
-        ]}
+        data={data}
       />
+      <LineAnnotation dataValues={[{ dataValue: 0 }]} id="baseline" domainType={AnnotationDomainType.YDomain} />
     </Chart>
   );
 };