Component | Line: Support interpolated dashed line for missing values

packages/angular/src/components/line/line.component.ts

@@ -121,6 +121,12 @@ export class VisLineComponent<Datum> implements LineConfigInterface<Datum>, Afte
 
   /** Optional link cursor. Default: `null` */
   @Input() cursor?: StringAccessor<Datum[]>
+
+  /** Enable interpolated line where data points are missing or fallbackValue is used.
+   * You can customize the line's appearance with `--vis-line-gapfill-stroke-dasharray`
+   * and `--vis-line-gapfill-stroke-opacity` CSS variables.
+   * Default: `false` */
+  @Input() interpolateMissingData: boolean
   @Input() data: Datum[]
 
   component: Line<Datum> | undefined
@@ -142,8 +148,8 @@ export class VisLineComponent<Datum> implements LineConfigInterface<Datum>, Afte
   }
 
   private getConfig (): LineConfigInterface<Datum> {
-    const { duration, events, attributes, x, y, id, color, xScale, yScale, excludeFromDomainCalculation, curveType, lineWidth, lineDashArray, fallbackValue, highlightOnHover, cursor } = this
-    const config = { duration, events, attributes, x, y, id, color, xScale, yScale, excludeFromDomainCalculation, curveType, lineWidth, lineDashArray, fallbackValue, highlightOnHover, cursor }
+    const { duration, events, attributes, x, y, id, color, xScale, yScale, excludeFromDomainCalculation, curveType, lineWidth, lineDashArray, fallbackValue, highlightOnHover, cursor, interpolateMissingData } = this
+    const config = { duration, events, attributes, x, y, id, color, xScale, yScale, excludeFromDomainCalculation, curveType, lineWidth, lineDashArray, fallbackValue, highlightOnHover, cursor, interpolateMissingData }
     const keys = Object.keys(config) as (keyof LineConfigInterface<Datum>)[]
     keys.forEach(key => { if (config[key] === undefined) delete config[key] })
 

packages/dev/src/examples/xy-components/line/multi-patchy-line/index.tsx

@@ -0,0 +1,82 @@
+import React, { useCallback, useEffect, useState } from 'react'
+import { VisAxis, VisBulletLegend, VisBulletLegendSelectors, VisCrosshair, VisLine, VisScatter, VisTooltip, VisXYContainer } from '@unovis/react'
+import { BulletLegendItemInterface, BulletShape, NumericAccessor, colors, CurveType } from '@unovis/ts'
+
+import { ExampleViewerDurationProps } from '@src/components/ExampleViewer'
+
+export const title = 'Interpolated Multi-Line Chart'
+export const subTitle = 'With interactive bullet legend'
+
+const n = undefined
+const layers: Record<string, (number | undefined | null)[]> = {
+  y0: [3, 5, 2, 5, n, 3, 4, 5, 4, 2, 5, 2, 4, 2, n, 5],
+  y1: [2, 1, n, 2, 2, n, 1, 3, 2, n, 1, 4, 6, 4, 3, 2],
+  y2: [5, 6, 7, n, 5, 7, 8, 7, 9, 6, n, 5, n, n, 9, 7],
+  y3: [9, n, n, 8, n, n, 5, 6, 5, 5, 4, 3, 2, 1, 2, 0],
+}
+
+type Datum = Record<keyof typeof layers, number> & { x: number }
+
+const keys = Object.keys(layers) as (keyof Datum)[]
+const data = Array.from({ length: layers.y0.length }, (_, i) => ({
+  x: i,
+  ...(keys.reduce((o, k) => ({ ...o, [k]: layers[k][i] }), {})),
+}))
+
+export const component = (props: ExampleViewerDurationProps): JSX.Element => {
+  const x: NumericAccessor<Datum> = d => d.x
+  const [y, setY] = useState<NumericAccessor<Datum>[]>()
+  const [color, setColor] = useState<string[]>([])
+
+  const [legendItems, setLegendItems] = useState(
+    keys.map((name, i) => ({ name, inactive: false, color: colors[i], cursor: 'pointer' }))
+  )
+
+  useEffect(() => {
+    const updated = legendItems.reduce((obj, item) => {
+      if (!item.inactive) obj.colors.push(item.color)
+      obj.ys.push(d => (item.inactive ? null : d[item.name]))
+      return obj
+    }, { colors: new Array<string>(), ys: new Array<NumericAccessor<Datum>>() })
+    setY(updated.ys)
+    setColor(updated.colors)
+  }, [legendItems])
+
+  const updateItems = useCallback((_: BulletLegendItemInterface, index: number) => {
+    const newItems = [...legendItems]
+    newItems[index].inactive = !newItems[index].inactive
+    setLegendItems(newItems)
+  }, [legendItems])
+
+  const tooltipTemplate = useCallback((d: Datum): string => legendItems.map(item => `
+    <div style="font-size:12px;${item.inactive ? 'text-decoration:line-through;opacity:0.7;color:#ccc">' : '">'}
+      <span style="color:${item.color};font-weight:${item.inactive ? '400' : '800'};">${item.name}</span>: ${d[item.name] ?? '-'}
+    </div>`
+  ).join(''), [legendItems])
+
+  return (
+    <div style={{ margin: 50 }}>
+      <style>{`
+          .square-legend .${VisBulletLegendSelectors.item} {
+            --vis-legend-item-spacing: 10px;
+            padding: 2px 4px;
+          }
+          .line-legend .${VisBulletLegendSelectors.bullet} { width: 16px !important; }
+          .line-legend .${VisBulletLegendSelectors.bullet} path { stroke-dasharray: 5 3; }
+
+        `}</style>
+      <div style={{ display: 'flex', width: 'max-content', padding: '10px 10px 0px 35px' }}>
+        <VisBulletLegend className='square-legend' items={legendItems} bulletShape={BulletShape.Square} onLegendItemClick={updateItems}/>
+        <VisBulletLegend className='line-legend' items={[{ name: 'No data', color: '#5558', shape: 'line' }]} />
+      </div>
+      <VisXYContainer yDomain={[0, 10]} data={data} height={400} duration={props.duration}>
+        <VisLine lineWidth={2} curveType={CurveType.Linear} x={x} y={y} color={color} interpolateMissingData/>
+        <VisScatter size={2} x={x} y={y} color={color}/>
+        <VisCrosshair template={tooltipTemplate} color={color}/>
+        <VisTooltip/>
+        <VisAxis type='x' tickFormat={(d: number) => `0${(Math.floor(d / 6)) + 1}:${d % 6}0pm`}/>
+        <VisAxis type='y'/>
+      </VisXYContainer>
+    </div>
+  )
+}

packages/dev/src/examples/xy-components/line/patchy-line/index.tsx

@@ -0,0 +1,85 @@
+import React, { useState } from 'react'
+import { VisXYContainer, VisLine, VisAxis, VisScatter, VisCrosshair, VisTooltip, VisAnnotations } from '@unovis/react'
+import { CurveType } from '@unovis/ts'
+
+import { ExampleViewerDurationProps } from '@src/components/ExampleViewer'
+
+import s from './style.module.css'
+
+export const title = 'Patchy Line Chart'
+export const subTitle = 'Various test cases'
+
+type TestCase = {
+  title: string;
+  data: (number | undefined | null)[];
+}
+
+const testCases: TestCase[] = [
+  { title: 'Gaps in middle', data: [3, 1, undefined, 7, undefined, 1, 1, undefined, 0.5, 4] },
+  { title: 'Longer gaps', data: [2, 3, undefined, undefined, undefined, 12, 10, undefined, undefined, 2] },
+  { title: 'Gaps at ends', data: [7, undefined, 9, 10, 7, 4, 5, 2, undefined, 10] },
+  { title: 'Gaps at true ends', data: [undefined, 2, 10, 4, 5, 2, 6, 2, 3, undefined] },
+  { title: 'Gaps surrounding single point', data: [5, 3, 6, undefined, 2, undefined, 10, 8, 9, 5] },
+  { title: 'All undefined', data: [undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined] },
+  { title: 'Single point', data: [undefined, undefined, undefined, undefined, 10, undefined] },
+  { title: 'Missing every other point', data: [3, undefined, 12, undefined, 7, undefined, 5, undefined, 12] },
+  { title: 'Includes undefined and null values', data: [3, 5, undefined, 6, 7, null, 9, 10, undefined, 4] },
+
+]
+
+export const component = (props: ExampleViewerDurationProps): JSX.Element => {
+  type Datum = Record<string, number>
+  const combined = Array.from({ length: 10 }, (_, i) => ({
+    x: i,
+    ...(testCases.reduce((obj, d, j) => ({
+      ...obj,
+      [`y${j}`]: d.data[i],
+    }), {})),
+  }))
+  const x = (d: Datum): number => d.x
+  const getY = (i: number) => (d: Datum) => d[`y${i}`]
+
+  const fallbacks = [undefined, 0, 5, 10]
+  const [fallbackValue, setFallbackValue] = useState(fallbacks[0])
+  const [interpolation, setInterpolation] = useState(true)
+  const [showScatter, setShowScatter] = useState(true)
+
+  return (
+    <div className={s.patchyLineExample}>
+      <div className={s.inputs}>
+        <label>
+          Fallback value:
+          <select onChange={e => setFallbackValue(fallbacks[Number(e.target.value)])}>
+            {fallbacks.map((o, i) => <option value={i}>{String(o)}</option>)}
+          </select>
+        </label>
+        <label>
+          Interpolate:<input type='checkbox' checked={interpolation} onChange={e => setInterpolation(e.target.checked)}/>
+        </label>
+        <label>
+          Show Scatter: <input type='checkbox' checked={showScatter} onChange={e => setShowScatter(e.target.checked)}/>
+        </label>
+      </div>
+      <div className={s.singleLines}>
+        {testCases.map((val, i) => (
+          <VisXYContainer<Datum> data={combined} key={i} xDomain={[-0.2, 9.2]} yDomain={[0, 15]} height={200} width='100%'>
+            <VisAnnotations items={[{ content: val.title, x: '50%', y: 0, textAlign: 'center' }]}/>
+            <VisLine
+              curveType={CurveType.Linear}
+              duration={props.duration}
+              fallbackValue={fallbackValue}
+              interpolateMissingData={interpolation}
+              x={x}
+              y={getY(i)}
+            />
+            {showScatter && <VisScatter excludeFromDomainCalculation size={2} x={x} y={d => getY(i)(d) ?? undefined}/>}
+            <VisCrosshair template={(d: Datum) => `${d.x}, ${getY(i)(d)}`} color='var(--vis-color0)' strokeWidth='1px'/>
+            <VisTooltip/>
+            <VisAxis type='x'/>
+            <VisAxis type='y' domainLine={false}/>
+          </VisXYContainer>
+        ))}
+      </div>
+    </div>
+  )
+}

packages/dev/src/examples/xy-components/line/patchy-line/style.module.css

@@ -0,0 +1,22 @@
+.patchyLineExample {
+  width: 100%;
+}
+
+.inputs {
+  font-family: 'Courier New', Courier, monospace;
+  font-size: smaller;
+  margin-bottom: 12px;
+}
+
+.inputs > label {
+  display: flex;
+  align-items: center;
+}
+
+.singleLines {
+  display: grid;
+  width: 100%;
+  grid-template-columns: repeat(3, 1fr);
+  column-gap: 10px;
+}
+

packages/ts/src/components/line/config.ts

@@ -24,6 +24,11 @@ export interface LineConfigInterface<Datum> extends XYComponentConfigInterface<D
   highlightOnHover?: boolean;
   /** Optional link cursor. Default: `null` */
   cursor?: StringAccessor<Datum[]>;
+  /** Enable interpolated line where data points are missing or fallbackValue is used.
+   * You can customize the line's appearance with `--vis-line-gapfill-stroke-dasharray`
+   * and `--vis-line-gapfill-stroke-opacity` CSS variables.
+   * Default: `false` */
+  interpolateMissingData?: boolean;
 }
 
 export const LineDefaultConfig: LineConfigInterface<unknown> = {
@@ -34,4 +39,5 @@ export const LineDefaultConfig: LineConfigInterface<unknown> = {
   fallbackValue: undefined,
   highlightOnHover: false,
   cursor: null,
+  interpolateMissingData: false,
 }

packages/ts/src/components/line/index.ts

@@ -83,23 +83,48 @@ export class Line<Datum> extends XYComponentCore<Datum, LineConfigInterface<Datu
     const lineData: LineData[] = yAccessors.map(a => {
       const ld: LineDatum[] = data.map((d, i) => {
         const rawValue = getNumber(d, a, i)
+
         // If `rawValue` is not numerical or if it's not finite (`NaN`, `undefined`, ...), we replace it with `config.fallbackValue`
         const value = (isNumber(rawValue) || (rawValue === null)) && isFinite(rawValue) ? rawValue : config.fallbackValue
+        const defined = config.interpolateMissingData
+          ? (isNumber(rawValue) || (rawValue === null)) && isFinite(rawValue)
+          : isFinite(value)
+
         return {
           x: lineDataX[i],
           y: this.yScale(value ?? 0),
-          defined: isFinite(value),
+          defined,
           value,
         }
       })
-
       const defined = ld.reduce((def, d) => (d.defined || def), false)
+
+      let validGap = false
+      const gaps = ld.reduce((acc, d, i) => {
+        // Gaps include fallback values if configured.
+        if (!d.defined && isFinite(config.fallbackValue)) {
+          acc.push({ ...d, defined: true })
+        }
+
+        if (!d.defined && !validGap) validGap = true
+
+        const isEndpoint = (i > 0 && !ld[i - 1].defined) || (i < ld.length - 1 && !ld[i + 1].defined)
+        if (d.defined && isEndpoint) {
+          // If no undefined points have been found since the last endpoint, we insert one to enforce breaks between adjacent gaps.
+          if (!validGap) acc.push({ ...d, defined: false })
+          acc.push(d)
+          validGap = false
+        }
+        return acc
+      }, [])
+
       // If the line consists only of `null` values, we'll still render it but it'll be invisible.
       // Such trick allows us to have better animated transitions.
       const visible = defined && ld.some(d => d.value !== null)
       return {
         values: ld,
         defined,
+        gaps,
         visible,
       }
     })
@@ -123,12 +148,18 @@ export class Line<Datum> extends XYComponentCore<Datum, LineConfigInterface<Datu
       .attr('class', s.lineSelectionHelper)
       .attr('d', this._emptyPath())
 
+    linesEnter.append('path')
+      .attr('class', s.interpolatedPath)
+      .attr('d', this._emptyPath())
+      .style('opacity', 0)
+
     const linesMerged = linesEnter.merge(lines)
     linesMerged.style('cursor', (d, i) => getString(data, config.cursor, i))
     linesMerged.each((d, i, elements) => {
       const group = select(elements[i])
       const linePath = group.select<SVGPathElement>(`.${s.linePath}`)
       const lineSelectionHelper = group.select(`.${s.lineSelectionHelper}`)
+      const lineGaps = group.select(`.${s.interpolatedPath}`)
 
       const isLineVisible = d.visible
       const dashArray = getValue<Datum[], number[]>(data, config.lineDashArray, i)
@@ -153,6 +184,18 @@ export class Line<Datum> extends XYComponentCore<Datum, LineConfigInterface<Datu
       lineSelectionHelper
         .attr('d', svgPathD)
         .attr('visibility', isLineVisible ? null : 'hidden')
+
+      if (hasUndefinedSegments && config.interpolateMissingData) {
+        smartTransition(lineGaps, duration)
+          .attr('d', this.lineGen(d.gaps))
+          .attr('stroke', getColor(data, config.color, i))
+          .attr('stroke-width', config.lineWidth - 1)
+          .style('opacity', 1)
+      } else {
+        lineGaps.transition()
+          .duration(duration)
+          .style('opacity', 0)
+      }
     })
 
     smartTransition(lines.exit(), duration)

packages/ts/src/components/line/style.ts

@@ -5,6 +5,10 @@ export const globalStyles = injectGlobal`
     --vis-line-cursor: default;
     --vis-line-stroke-dasharray: none;
     --vis-line-stroke-dashoffset: 0;
+
+    --vis-line-gapfill-stroke-dasharray: 2 3;
+    --vis-line-gapfill-stroke-opacity: 0.8;
+    --vis-line-gapfill-stroke-dashoffset: 0;
   }
 `
 
@@ -35,3 +39,11 @@ export const lineSelectionHelper = css`
 export const dim = css`
   opacity: 0.2;
 `
+
+export const interpolatedPath = css`
+  label: interpolated-path;
+  fill: none;
+  stroke-dasharray: var(--vis-line-gapfill-stroke-dasharray);
+  stroke-dashoffset: var(--vis-line-gapfill-stroke-dashoffset);
+  stroke-opacity: var(--vis-line-gapfill-stroke-opacity);
+`

packages/ts/src/components/line/types.ts

@@ -1,3 +1,3 @@
 /** Data type for Line Generator: [x, y, defined] */
 export type LineDatum = { x: number; y: number; value: number | null | undefined; defined: boolean }
-export type LineData = { values: LineDatum[]; defined: boolean; visible: boolean }
+export type LineData = { values: LineDatum[]; gaps: LineDatum[]; defined: boolean; visible: boolean }

packages/website/docs/xy-charts/Line.mdx

@@ -53,6 +53,7 @@ Similar to [mutlti-color configuration](#for-multiple-lines), you can provide an
 customize each line.
 
 ## Dealing with missing data
+### Fallback Value
 In the case of missing data (when the data values are `undefined`, `NaN`, `''`, etc ...), you can assign a fallback value
 for _Line_ using the `fallbackValue` config property. The default value is `undefined`, which means that the line will
 break in the areas of no data and continue when the data appears again. If you set `fallbackValue` to `null`, the values
@@ -70,6 +71,25 @@ Consider the following example, where the dataset contains `undefined` values ov
   defaultValue={7}
   showAxes/>
 
+### Line Interpolation
+Alternatively, you can set the `interpolateMissingData` property to `true` to fill in the data gaps with a dashed line.
+If `fallbackValue` is set, those values will be plotted on the inteprolated line.
+Otherwise, it will be a smooth curve between defined points, like below:
+
+<XYWrapper {...lineProps()}
+  data={[1, 3, 4, undefined, undefined, undefined, 5, 7, 9, 6].map((y, x) => ({ x, y }))}
+  showAxes
+  interpolateMissingData={true}
+/>
+
+You can customize the appearance of of the interpolated line with the following CSS varibles:
+
+```css
+--vis-line-gapfill-stroke-dasharray: 2 3;
+--vis-line-gapfill-stroke-opacity: 0.8;
+--vis-line-gapfill-stroke-dashoffset: 0;
+```
+
 ## Events
 ```ts
 import { Line } from '@unovis/ts'