@visa/line-chart

<line-chart
  accessibility = {...}
  data = {[{"date":"2016-01-01T00:00:00.000Z","category":"Restaurant","value":120},{data}]}
  valueAccessor = {"value"}
  ordinalAccessor = {"date"}
  seriesAccessor = {"category"}
/>

# Installation Steps

• Using npm

  $ npm i @visa/line-chart

• Using yarn

  $ yarn add @visa/line-chart

# Props Documentation

# Base Props <>

| Name | Type | Default Value(s) | Description | | --------------------- | -------------------------------------------------- | -------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------- | | height | number | 300 | Height in px of the chart container | | width | number | 650 | Width in px of the chart container | | mainTitle | string | 'Line Chart Title' | The dynamic tag of title for the chart (or you can create your own separately). See highestHeadingLevel prop for how tags get assigned. | | subTitle | string/ISubTitleType | 'This is a subtitle' | The dynamic tag for a sub title for the chart (or you can create your own separately). See highestHeadingLevel prop for how tags get assigned. | | highestHeadingLevel | string/number | 'h2' | Sets the heading level (which also sets sublevels) for the chart. "p", "span", and "div" are also valid. |

ISubTitleType Definition

| Name | Type | Default Value(s) | Description | | ------------------- | -------- | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | text | string | ‘’ | Text of the subtitle. | | keywordsHighlight | object[] | ‘’ | Data used to create highlighted words in the subtitle, an array of objects which includes text, color and index keys. text correspond to one more multiple words/numbers as a single string in the subtitle text. color takes a HEX color string. index takes a number, if not specified all occurrences of the text will be highlighted. |

# Data Props <>

| Name | Type | Default Value(s) | Description | | ----------------- | -------------------- | -------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ordinalAccessor | string | 'label' | Key used to determine line's categorical property. | | valueAccessor | string | 'value' | Key used to determine line's numeric property. Note: see Line interpolation behavior below for further details on behavior of lines based on valueAccessor data passed. | | seriesAccessor | string | 'series' | Key used to determine series. | | uniqueID | string | undefined | ID used to identify chart (must be unique per chart), helpful for validation messages. Defaults to UUID v4 standard. | | data | object[] | undefined | Data used to create chart, an array of objects which includes keys that map to above accessors. | | secondaryLines | object (custom type) | ISecondaryType | Array of values used to classify series as secondary |

ISecondaryType Definition

| Name (secondaryLines.) | Type | Default Value(s) | Description | | ---------------------- | -------- | ---------------- | -------------------------------------------------------- | | keys | string[] | [] | Assign keys of secondary lines. | | showDataLabel | boolean | true | Sets the visibility of data labels on secondary lines. | | showSeriesLabel | boolean | true | Sets the visibility of series labels on secondary lines. | | opacity | number | 1 | Sets the opacity of secondary lines. |

Line interpolation behavior

The way data is sent to line-chart will have significant impacts on how the component will render lines. Here are three main scenarios you can take advantage of to ensure lines are rendered as need be for your use case.

| Scenario | Description | Expected Result | | ---------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | All values present and passed to chart | The data object array passed has a valid numeric value or valueAccessor for each ordinalAccessor, and seriesAccessor value. | Each point on line is rendered. | | Missing values *not* passed to chart | The data object array passed has a valid numeric value or valueAccessor for some ordinalAccessor, and seriesAccessor values. E.g., null valueAccessor values are filtered, before sending data object to chart. | Lines will connect/interpolate over data which is not sent to chart. | | Missing values *are* passed to chart | The data object array passed has a valid numeric value or valueAccessor for some ordinalAccessor, and seriesAccessor values. Also, null or undefined values are passed for any missing data. E.g., null valueAccessor values are included when sending data object to chart. | Lines will break to reflect the null or undefined data passed. |

# Accessibility Props <>

| Name | Type | Default Value(s) | Description | | --------------- | -------------------- | ------------------------------------------------ | ------------------------------------------------------------------------------------- | | accessibility | object (custom type) | IAccessibilityType | Manages messages and settings for chart accessibility, see object definition below. |

IAccessibilityType Definition

| Name (accessibility.) | Type | Default Value(s) | Description | | ---------------------------- | ---------------------------------------- | --------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | longDescription | string | '' | Use this to add a helpful description of the chart. | | executiveSummary | string | '' | Use this to describe the biggest takeaway of the chart. | | purpose | string | '' | Use this to describe the purpose of this particular chart. | | contextExplanation | string | '' | Use this to explain any controls or content on your page that affect or are affected by this chart. | | title | string | '' | Gives the chart an alternate title to be used by screen readers. | | elementDescriptionAccessor | string | '' | Optional key used to add an additional description to any element, from your data. | | statisticalNotes | string | '' | Use this to provide any statistical explanations, such as trends, clusters, patterns, or outliers. | | structureNotes | string | '' | Use this to describe special visual features of the chart, such as sorting, color grouping, etc. | | includeDataKeyNames | boolean | false | If true, includes data key names in voice over description of each element. EG "Year over year growth: 5.6%" instead of just "5.6%" | | hideDataTableButton | boolean | false | If true, hides the data table button (but it is still available to screen reader users). | | disableValidation | boolean | false | If true, disables validations of accessibility props for this chart. Validation is intended to be used during development; upon completion, validation should be disabled. | | elementsAreInterface | any/boolean | null | Defaults to null. Set to true if interacting with the elements in this chart affects your application. Otherwise, must be set to false. | | onChangeFunc | function | undefined | Custom event listener (changeFunc) that enables dev to control accessibility page experience when chart data updates. | | showSmallLabels | boolean | false | Defaults to false. Set to true if you would like to display labels on small elements that are likely to overlap. Note, this could impact accessibility of your graphic. | | hideStrokes | boolean | false | Defaults to false. Set to true if you would like to remove automated stroke outlines from the chart, note, this could impact accessibility of your graphic. | | hideTextures | boolean | false | Defaults to false. Set to true if you would like to remove textures from the chart, note, this could impact accessibility of your graphic. | | keyboardNavConfig | IKeyConfig | { disabled: false } | Defaults disabled to false. May be set to true if accessibility.elementsAreInterface = false and suppressEvents = true. This will disable keyboard navigation and simplify chart instructions for screen reader users. | | showExperimentalTextures | boolean | false | Defaults to false. Set to true if you would like leverage our textures which are still undergoing research and development. |

// accessibility = { ...accessibility, onChangeFunc: d => changeHandler(d)}
// example of setting updates on page based on changeFunc custom events
const changeHandler = d => {
  if (d.updated && (d.removed || d.added)) {
    let updates = 'The line chart has ';
    if (d.removed) {
      updates += 'removed ' + d.removed + ' point' + (d.removed > 1 ? 's ' : ' ');
    }
    if (d.added) {
      updates += (d.removed ? 'and ' : '') + 'added ' + d.added + (d.removed ? '' : d.added > 1 ? ' points' : ' point');
    }
    setChartUpdates(updates);
  } else if (d.updated) {
    const newUpdate = "The chart's data has changed, but no points were removed or added.";
    setChartUpdates(
      newUpdate !== chartUpdates
        ? newUpdate
        : "The chart's data has changed again, but no data points were removed or added."
    );
  }
};

# Localization Props <>

| Name | Type | Default Value(s) | Description | | -------------- | -------------------- | ----------------------------------------------- | ------------------------------------------------------------------------------------ | | localization | object (custom type) | ILocalizationType | Manages messages and settings for chart localization, see object definition below. |

ILocalizationType Definition

| Name (localization.) | Type | Default Value(s) | Description | | -------------------- | ------------- | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | language | string/object | en | Use this to add a language to a chart. This can be string value like en or valid translation object. | | numeralLocale | string/object | US | Use this to add a numerical locale to a chart. This can be string value like US or valid numeralLocale object. | | overwrite | boolean | false | Use this to describe the purpose of this particular chart. | | skipValidation | boolean | false | If true, disables validations of localization props for this chart. Validation is intended to be used during development; upon completion, validation should be disabled. |

# Annotation Props <>

| Name | Type | Default Value(s) | Description | | ------------- | -------------------- | ---------------- | ------------------------------------------------------------------------------------------------------- | | annotations | array[{annotations}] | [] | Adds annotations to the chart, see d3-svg-annotation by Susie Lu. |

annotations object definition

annotations is an array of objects which needs to have the following properties within them. See the detailed api specifications from d3-svg-annotation, along with additional properties layered on top of that work, documented below.

| Name | Type | Default Value(s) | Description | | -------------------------- | ------ | ---------------- | ------------------------------------------------------------------------------ | | accessibilityDescription | string | undefined | Sets the accessibility description for the annotation for screen reader users. |

# Axis Props <>

| Name | Type | Default Value(s) | Description | | ------------------ | -------------------- | --------------------------------------- | ----------------------------------------------------------------------- | | xAxis | object (custom type) | IAxisType | Manages settings for the chart's x axis, see object definition below. | | yAxis | object (custom type) | IAxisType | Manages settings for the chart's y axis, see object definition below. | | minValueOverride | number | undefined | Overrides the calculated default min value. | | maxValueOverride | number | undefined | Overrides the calculated default max value. | | showBaselineX | boolean | false | When selected, shows the x baseline | | wrapLabel | boolean | true | When selected, wraps axis labels. |

IAxisType Definition

| Name (xAxis./yAxis.) | Type | Default Value(s) | Description | | -------------------- | ------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------ | | visible | boolean | true | Toggles the visibility of the axis. | | gridVisible | boolean | true | Toggles the visibility of the axis grid. | | label | string | 'X Axis' | Sets the label for the axis. | | unit | string | '' or 'month' | Sets the unit of padding for the axis when accessor is a date. | | format | string | '' or '%b %y' or '0[.][0][0]a' | Sets the formatting for axis elements, EG %b, refer to d3-time-format and numeral.js. | | tickInterval | number | 1 | Can be used to reduce the frequency of axis ticks. This number sets the interval of axis ticks that are shown. |

# Event Props <>

Events in stencil.js dispatch Custom DOM events for other components to handle, we use Stencil's @Event() decorator to emit events (click, hover, mouseOut) from end user activity on our charts.

| Name | Type | Default Value(s) | Description | | ----------------------- | -------------------- | --------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | suppressEvents | boolean | false | Suppresses and disables click, hover and mouseOut event emitters. Setting to true can increase performance for non-interactive charts. | | cursor | string | 'default' | Changes pointer type during mouse over on elements. Valid values are 'default' or 'pointer'. | | onClickEvent | function | undefined | When clickEvent event occurs (e.g., mouse/keyboard click on chart geometry), this event handler will be called with the custom event object (e.g., e), containing data and target node at e.detail {data: d, target: n}. You will need to construct your own functionality of what actions to take within the callback. | | clickHighlight | object[] | [] | Data used to track chart selections, an array of objects which includes keys that map to above accessors. | | clickStyle | object (custom type) | IClickStyleType | Sets the styling of elements when they are selected, see object definition below. | | onHoverEvent | function | undefined | When hoverEvent event occurs (e.g., mouse hover/keyboard focus on chart geometry), this event handler will be called with the custom event object (e.g., e), containing data and target node at e.detail {data: d, target: n}. You will need to construct your own functionality of what actions to take within the callback. | | onMouseOutEvent | function | undefined | When mouseOutEvent event occurs (e.g., mouse/keyboard blur on chart geometry), this event handler will be called, and has no data object. You will need to construct your own functionality of what actions to take within the callback. | | hoverHighlight | object | {} | Datum object used to track active chart element, the object should include keys that map to above accessors. | | hoverStyle | object (custom type) | IHoverStyleType | Sets the styling of elements when they are hovered/focused, see object definition below. | | interactionKeys | string[] | [] | Sets the column names of data to interact with. | | hoverOpacity | number | 1 | Sets opacity of inactive elements when hovering/focused on a chart geometry. | | onInitialLoadEvent | function | undefined | When initalLoad event occurs (e.g., chart is mounted to window), this event handler will be called with the custom event object (e.g., e), containing the corresponding chartID at e.detail. You will need to construct your own functionality of what actions to take within the callback. | | onInitialLoadEndEvent | function | undefined | When initalLoadEnd event occurs (e.g., chart has been mounted to window), this event handler will be called with the custom event object (e.g., e), containing the corresponding chartID at e.detail. You will need to construct your own functionality of what actions to take within the callback. | | onDrawStartEvent | function | undefined | When drawStart event occurs (e.g., chart render function is called), this event handler will be called with the custom event object (e.g., e), containing the corresponding chartID at e.detail. You will need to construct your own functionality of what actions to take within the callback. | | onDrawEndEvent | function | undefined | When drawEnd event occurs (e.g., chart's stencil lifecycle completes), this event handler will be called with the custom event object (e.g., e), containing the corresponding chartID at e.detail. You will need to construct your own functionality of what actions to take within the callback. | | onTransitionEndEvent | function | undefined | When transitionEnd event occurs (e.g., chart geometry's transition lifecycle completes), this event handler will be called with the custom event object (e.g., e), containing the corresponding chartID at e.detail. You will need to construct your own functionality of what actions to take within the callback. |

IClickStyleType Definition

| Name | Type | Default Value(s) | Description | | ------------- | ------ | ---------------- | -------------------------------------------------------------------------------------------- | | color | string | '' | Sets the color of the clicked element (requires clickHighlight to be valid and sent). | | strokeWidth | number | 2 | Sets the stroke width of the clicked element (requires clickHighlight to be valid and sent). |

IHoverStyleType Definition

| Name | Type | Default Value(s) | Description | | ------------- | ------ | ---------------- | -------------------------------------------------------------------------------------------- | | color | string | '' | Sets the color of the hovered element (requires hoverHighlight to be valid and sent). | | strokeWidth | number | 2 | Sets the stroke width of the hovered element (requires hoverHighlight to be valid and sent). |

// example of interactivity code
// note this only tracks a single click, you need your own logic to build the array of currnet selections made by user and then pass that result back to chart
//...
const clickHandler = evt => {
  const d = evt.detail.data; // data is located here
  const t = evt.detail.target; // chart mark/label clicked is located here

  this.currentClickedElement = [d]; // this is passed to clickHighlight prop
};

const hoverHandler = evt => {
  const d = evt.detail.data; // data is located here
  const t = evt.detail.target; // chart mark/label clicked is located here

  this.currentHoveredElement = d; // this is passed to hoverHighlight prop
};

const mouseOutHandler = evt => {
  this.currentHoveredElement = ''; // this is passed to hoverHighlight prop
};

// an example of calling these from within a stencil.js component
<line-chart
  data={[{ data }]}
  valueAccessor={'value'}
  ordinalAccessor={'date'}
  seriesAccessor={'category'}
  interactionKeys={['category']}
  onClickEvent={this.onClickEvent}
  clickHighlight={this.currentClickedElement}
  clickStyle={this.clickStyle}
  onHoverEvent={this.onHoverEvent}
  onMouseOutEvent={this.onMouseOut}
  hoverHighlight={this.currentHoveredElement}
  hoverStyle={this.hoverStyle}
/>;
//...

# Label Props <>

| Name | Type | Default Value(s) | Description | | -------------- | -------------------- | ----------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | dataLabel | object (custom type) | IDataLabelType | Controls visibility, styling and placement of data labels, see object definition below. | | dataKeyNames | object | undefined | Object that contains mapping of data keys (e.g., accessors) and user friendly names of the data fields. This prop can be used to enable translation of data keys between languages, or just provide a meaningful name for data elements within a chart. The key:value pairs in this object will effect tooltips, data table, aria labels, axes, etc. Anywhere in chart where data key may be exposed to consumers. | | seriesLabel | object (custom type) | ISeriesLabelType | Controls visibility, styling and placement of series labels, see object definition below. | | legend | object (custom type) | ILegendType | Controls visibility and label of the chart legend, see object definition below. | | showTooltip | boolean | true | Toggles whether to display the tooltip on hover/focus on chart geometries. | | tooltipLabel | object (custom type) | ITooltipLabelType | Controls visibility, content and format of the chart tooltip, see object definition below. |

IDataLabelType Definition

| Name | Type | Default Value(s) | Description | | -------------------- | ------- | ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | labelAccessor | string | '' | Key used to determine label's property. | | visible | boolean | true | Toggles the visibility (opacity) of the data labels. | | placement | string | 'top' | Sets the placement of the data label, accepts 'top' or 'bottom'. Placement option 'auto' leverages the resolveLabelCollision algorithm and places labels without overlaps in available space on the chart. | | format | string | '0[.][0][0]a' | Sets the formatting for the data labels, EG %b, refer to d3-time-format and numeral.js. | | collisionHideOnly | boolean | false | Toggles whether to run resolveLabelCollision algorithm and hide labels if collision is detected (vs hide and then place). This is overridden by placement being set to auto. | | collisionPlacement | string | 'all' | Sets the placement of the data label when resolveLabelCollision algorithm is run (dataLabel.placement must be 'auto'). Examples of values are 'all', 'top', 'middle', 'bottom', 'left' and 'right'. |

ISeriesLabel Definition

| Name | Type | Default Value(s) | Description | | ------------------- | -------- | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | label | string[] | [] | An array which determines the labels for each line, in order. | | visible | boolean | true | Toggles the visibility (opacity) of the series labels. | | placement | string | 'right' | Sets the placement of the series label, accepts 'left' or 'right'. Placement option 'auto' leverages the resolveLabelCollision algorithm and places labels without overlaps in available space on the chart. | | collisionHideOnly | boolean | false | Toggles whether to run resolveLabelCollision algorithm and hide series labels if collision is detected (vs hide and then place). This is overridden by placement being set to auto. |

ILegendType Definition

| Name | Type | Default Value(s) | Description | | ------------- | -------- | ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------- | | visible | boolean | true | Toggles the visibility (opacity/display) of the legend. | | interactive | boolean | false | Toggles the interactivity of the legend. | | format | string | '' | Sets the formatting for the legend labels, EG %b, refer to d3-time-format and numeral.js. | | labels | string[] | '' | An array that sets each label in the legend, in order. Passing empty string will populate legend labels directly from data values. |

ITooltipLabelType Definition

| Name | Type | Default Value(s) | Description | | --------------- | -------- | ---------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | labelAccessor | string[] | [] | An array that determines which property of the data is displayed in the tooltip. | | labelTitle | string[] | [] | An array that sets the title for each data property in the tooltip. | | format | string | '' | Sets the formatting for the data properties in the tooltip, EG %b, refer to d3-time-format and numeral.js. |

# Margin & Padding Props <>

| Name | Type | Default Value(s) | Description | | --------- | -------------------- | ------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- | | margin | object (custom type) | IBoxModelType | Margin between the subtitle and the chart area, or between the title and chart area if no subtitle is specified, see object definition below. | | padding | object (custom type) | IBoxModelType | Padding between plot area and axes lines, see object definition below. |

IBoxModelType Definition

| Name | Type | Default Value(s) | Description | | -------- | ------ | ---------------- | ------------------------------------------------------- | | top | number | height * 0.01 | Sets the top margin/padding for the chart container. | | bottom | number | height * 0.01 | Sets the bottom margin/padding for the chart container. | | left | number | width * 0.01 | Sets the top margin/padding for the chart container. | | right | number | width * 0.01 | Sets the top margin/padding for the chart container. |

# Style Props <>

| Name | Type | Default Value(s) | Description | | -------------- | -------- | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | colorPalette | string | 'diverging_RtoB' | Included color palettes can be found in our color utility. Overridden by colors. | | colors | string[] | undefined | Accepts array of color strings or color values to customize colors beyond our palettes Colors assigned in order. | | dotRadius | number | 4 | Sets the radius of data points, if visible. | | lineCurve | string | 'linear' | Sets the d3 curve of the line, accepts 'linear' or 'step'. Refer to d3-shape curve docs for more details. Note: VCC enables only select curve options from D3. | | showDots | boolean | true | When selected, makes data point dots visible. | | strokeWidth | string | '2' | Changes stroke width of series lines. |

# Reference Line Props <>

The referenceLines and referenceStyle props are currently deprecated and will ultimately be fully replaced with the annotation prop. For the time being, this prop will work, but will also not pass accessibility requirements.

| Name | Type | Default Value(s) | Description | | ---------------- | -------------------- | ------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | | referenceLines | object[] | [] | Data that sets the location and labeling of the reference line(s) see object definition below. ### IReferenceLineType | | referenceStyle | object (custom type) | IReferenceStyleType | Sets the styling of reference line(s) placed on the chart, see object definition below. ### IReferenceStyleType Definition |

IReferenceStyleType Definition

| Name | Type | Default Value(s) | Description | | ------------- | ------ | ---------------- | ----------------------------------------------------------------------- | | color | string | 'pri_grey' | Sets the color of the reference line. | | strokeWidth | number | 1 | Sets the stroke width of the reference line. | | opacity | number | 1 | Sets the opacity of the reference line. | | dashed | string | '' | Sets the dash array property of the path element of the reference line. |

referenceLines object definition

referenceLines is an array of objects which needs to have the following properties within them.

| Name | Type | Default Value(s) | Description | | ----------------------------- | ------- | ----------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | label | string | undefined | Sets the label to show for the reference line. | | labelPlacementHorizontal | string | Chart horizontal layout mode: left or middle or right. Chart vertical layout mode: top or bottom. | Sets the horizontal label placement for the reference line. | | labelPlacementVertical | string | Chart horizontal layout mode: left or right. Chart vertical layout mode: top or middle or bottom. | Sets the vertical label placement for the reference line. | | value | number | undefined | Sets the value where to place the reference line, per the axis. | | accessibilityDescription | string | undefined | Descriptive text for the reference line which will be provided to screen reader users via VCCs accessibility description's setAccessAnnotation utility. | | accessibilityDecorationOnly | boolean | undefined | When the reference line is decorative (e.g., does not provide any additional information), set accessibilityDecorationOnly to true to avoid unnecessary reference line content in VCCs accessibility descriptions. |