hermes-parallel-coordinates
v0.6.17
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A lightweight and fast canvas-based parallel coordinates chart library.
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Hermes Parallel Coordinates
A lightweight canvas-based parallel coordinates chart library.
Parallel coordinates are a common way of visualizing and analyzing high-dimensional datasets.
Check out the list of Demos to get an idea of the various capabilities and config options.
Or try out the Live Demo in a sandbox.
Screenshots
Standard parallel coordinates rendering with default options.
Filtering data on multiple dimensions. You can have multiple filters per dimension as well.
Chart drawn with bezier curves instead of the default straight lines.
Support for vertical layout with a simple config change of layout from horizontal
to vertical
.
Features
- Drag-and-drop dimensions.
- Support for dimension filters. Multiple filters per dimension supported.
- Support for linear, logarithmic and categorical dimension scales.
- Support for vertical layout.
- Auto redraw upon chart resize.
- Color scale and gradient based on a key dimension.
- Highly customizable styles:
- Axes: color, thickness, width (active and hover styles)
- Filters: color, thickness, stroke, fill (active and hover styles)
- Labels: font, color, position, angle (active and hover styles)
- Ticks: font, color, position, angle (active and hover styles)
- Fast render times.
API
Hermes
is a class. To use render the chart, simply create a new instance of Hermes
and pass in the necessary parameters.
new Hermes(
target: HTMLElement | string,
dimensions?: Hermes.Dimension[],
config?: RecursivePartial<Hermes.Config>,
data?: Hermes.Data,
);
Hermes Container
The container
can be an HTML element passed in directly or a query selector that matches an element. For example you can pass in #hermes
and Hermes will look for the element with the id
attribute set to hermes
and use that as a container for the chart rendering.
Hermes Data Format
The data format is of type Hermes.Data, which is an object with the dimension unique keys as the object key and a list of values for that dimension as the value. The expected data is defined as:
type Data = Record<DimensionKey, Primitive[]>;
A sample data input might look like...
const data = {
'weight': [ 155, 29, 6, 109 ],
'gender': [ 'm', 'm', 'u', 'f' ],
'is-adult': [ true, false, false, true ],
};
Hermes Target
The target
can be an HTML element passed in directly or a query selector that matches an element. For example you can pass in #hermes
and Hermes will look for the element with the id
attribute set to hermes
and use that as a container for the chart rendering.
Hermes Dimension
The dimensions definition is a list of Hermes.Dimension. A sample dimension definition might look like...
const dimensions = [
{
key: 'weight',
label: 'Weight',
type: Hermes.DimensionType.Linear,
},
{
categories: [ 'f', 'm', 'u' ],
key: 'gender',
label: 'Gender',
type: Hermes.DimensionType.Categorical,
},
{
categories: [ true, false ],
key: 'is-adult',
label: 'Is an adult?',
type: Hermes.DimensionType.Categorical,
},
];
Hermes Data Format
The data format is of type Hermes.Data, which is an object with the dimension unique keys as the object key and a list of values for that dimension as the value. The expected data is defined as:
type Data = Record<DimensionKey, Primitive[]>;
A sample data input might look like...
const data = {
'weight': [ 155, 29, 6, 109 ],
'gender': [ 'm', 'm', 'u', 'f' ],
'is-adult': [ true, false, false, true ],
};
key: string
This is a required unique identifier for the defined dimension. This is used internally for dimension ordering and when filters are created for a corresponding dimension.
label: string
The string label to display on the chart for the dimension.
type: 'categorical' | 'linear' | 'logarithmic'
This field specifies the dimension scale type. The 3 possible values are categorical
, linear
or logarithmic
. The corresponding TypeScript references are Hermes.DimensionType.Categorical
, Hermes.DimensionType.Linear
and Hermes.DimensionType.Logarithmic
.
categories: Primitive[] (optional)
If the dimension scale type is set to categorical
, this field needs to be defined. The data for categorical dimensions need to match a value in the categories
list. Some examples of categories
:
# boolean categories
categories: [ true, false ]
# numeric categories
categories: [ 1, 2, 4, 8, 16 ]
# string categories
categories: [ 'slow', 'medium', 'fast' ]
dataOnEdge: boolean (optional)
If unspecified, dataOnEdge
defaults to true
. When true
, the dimension scale ranges from the minimum data value to the maximum data value. For example, if for dimension loss
had data values ranging from 2.1
to 5.4
, the dimension scale will show 2.1
to 5.4
.
If disabled and set to false
, Hermes will try to find the nearest nice number for the extremes on the scale. The extremes are still based on the data value range. So for the same loss
example above, the dimension scale will instead show 2.0
to 5.5
or something similar.
logBase: whole number (optional)
If the dimension scale type is set to logarithmic
, logBase
can be set to determine what logarithmic base you wish the scale to be set. If this value is not provided, it defaults to logBase
of 10. Common log base values are 2 and 10.
reverse: boolean (optional)
The dimension axes are drawn vertically, the axis tick values increase from the bottom up. When drawn horizontally, the axis tick values increase from left to right. Setting the reverse
to true
will reverse the direction of the axis tick along the axes.
Hermes Config and Styles
The config provides control over the chart behavior, rendering, style and the ability to hook into key events. Hermes.Config provides a more up-to-date definition of the config.
General Config
direction: 'horizontal' default | 'vertical'
The direction the dimensions should be laid out. The direction can be set to horizontal
or vertical
. The horizontal
direction will draw the dimensions across the canvas with vertical axes. The vertical
direction will draw the dimensions top to bottom on the canvas with horizontal axes.
Hooks
onDimensionMove: (dimension: Dimension, newIndex: number, oldIndex: number) => void
Optional hook for when the order of dimensions changes via drag and drop. The callback is called during the drag and whenever dimensions required a swap, even before when the mouse is released. The data for the dimension that is dragged, the new index and the original index are returned.
onFilterChange: (filters: Filters) => void
Optional hook for when any filter changes. The callback is specifically called on the mouseup
event. The entire updated filters object is returned.
onFilterCreate: (filters: Filters) => void
Optional hook for when a filter is created. The newly create filter is returned.
onFilterMove: (filters: Filters) => void
Optional hook for when a filter is moved. The modified filter is returned.
onFilterRemove: (filters: Filters) => void
Optional hook for when a filter is removed via single click. Info for the removed filter is returned.
onFilterResize: (filters: Filters) => void
Optional hook for when a filter is resized. The modified filter is returned.
onReset: () => void
Optional hook for when the chart is reset via double click. The dimension order is reset back to the original order and the filters are cleared out.
onResize: (newSize: Size, oldSize: Size) => void
Optional hook for when the chart containing element is resized. The resize is detected using the ResizeObserver API, which observes the chart containing HTML element. When the element changes in size, this callback returns the new size and the original size.
Interactions
throttleDelayMouseMove (default 50)
The time interval in millisconds in which the mouse move event is allowed to propogate. For example, with the default 50ms, as the user moves the mouse cursor around, the mouse move event, the associated calculations and the rerenders are allowed to happen only every 50ms. The mouseup
handler performs all of the mousemove
event operations. So if this interval happens to be set to a very high number, where the mouseup
event occurs before a throttle
throttleDelayResize (default: 50)
The time interval in milliseconds in which the resize event is allowed to propagate. For example, with the default 50ms, as the user is changing the browser window that contains the chart, the resize event, the associated calculations and the rerenders are allowed to happen only every 50ms.
Style Options
axes
The axes
style options allows the dimension axes to be customized visually.
axis: AxisOptions
The axis
style impacts how each dimension axis is drawn and what the interactive area of the axis will be.
axis: {
// Adds a 15px to both the left and right (or above and below depending on the chart orientation) of the 1px wide axis for interactive area.
boundaryPadding: 15,
// Draws the +Infinity and -Infinity axis offset as a 2, 4 dashed lines.
infLineDash: [ 2, 4 ],
// Draws the +Infinity and -Infinity axis ticks 24px off from the axis ends.
infOffset: 24.0,
// Draws the axis as a 1px width line.
lineWidth: 1,
// Sets the NaN tick 24px off of the axis at the end.
nanGap: 24.0,
// Draws the axis with an opaque grey.
strokeStyle: 'rgba(147, 147, 147, 1.0)',
},
axisActve: StyleLine
The axisActive
style is in effect when the user is clicking on the axis to create or modify dimension filters.
axisActive: {
lineWidth: 3,
strokeStyle: 'rgba(99, 200, 255, 1.0)',
},
axisHover: StyleLine
The axisHover
style is in effect when the user hovers over the axis with the mouse pointer.
axisHover: {
lineWidth: 3,
strokeStyle: 'rgba(79, 180, 246, 1.0)',
},
filter: FilterOptions
The filter
style determines how the filters are drawn.
filter: {
cornerRadius: 2,
fillStyle: 'rgba(235, 100, 200, 1.0)',
strokeStyle: 'rgba(255, 255, 255, 1.0)',
width: 4,
},
filterActive: FilterOptions
The filterActive
style is in effect when the user clicks on the filter to interact with the filter.
filterActive: {
cornerRadius: 3,
fillStyle: 'rgba(255, 120, 220, 1.0)',
width: 8,
},
filterAxisHover: FilterOptions
The filterAxisHover
style is applied to filters on the axis the user is hovering over, but not directly hovering over the filters themselves.
filterAxisHover: {
cornerRadius: 2,
fillStyle: 'rgba(235, 100, 200, 1.0)',
width: 6,
},
filterHover: FilterOptions
The filterHover
style is in effect when the user is hovering over the filter.
filterHover: {
cornerRadius: 2,
fillStyle: 'rgba(235, 100, 200, 1.0)',
width: 8,
},
label: LabelOptions
The label
style determines how the tick labels ared drawn for the axis.
label: {
fillStyle: 'rgba(0, 0, 0, 1.0)',
font: 'normal 11px sans-serif',
lineWidth: 3,
offset: 4,
placement: ELabelPlacement.After,
strokeStyle: 'rgba(255, 255, 255, 1.0)',
},
labelActive: StyleText
The labelActive
style is in effect for the tick labels when axis is clicked on by the user.
labelActive: { fillStyle: 'rgba(0, 0, 0, 1.0)' },
labelHover: StyleText
The labelHover
style is in effect the tick labels when the user hovers over the axis.
labelHover: { fillStyle: 'rgba(0, 0, 0, 1.0)' },
tick: TickOptions
The tick
style determines how the tick marks on the axis are drawn.
tick: {
length: 4,
lineWidth: 1,
strokeStyle: 'rgba(147, 147, 147, 1.0)',
},
tickActive: StyleLine
The tickActive
style determines how the tick marks on the axis are drawn when the axis is active.
tickActive: { strokeStyle: 'rgba(99, 200, 255, 1.0)' },
tickHover: StyleLine
The tickHover
style determines how the tick marks on the axis are drawn when the user hovers over the axis.
tickHover: { strokeStyle: 'rgba(79, 180, 246, 1.0)' },
data
The data
style options allows for the chart series line to be styled. The most common line styles to change include the line color and the width of the line. This is represented by an object of StyleLine.
default: StyleLine
The default
style is used to draw all the chart lines. This is useful to provide a uniform style for all chart series. For example, the following default
style would draw all the series with a thickness of 1px wide and with an opaque light blue color.
default: {
lineWidth: 1,
strokeStyle: 'rgba(82, 144, 244, 1.0)',
},
filtered: StyleLine
The filtered
style is used to render lines NOT included in the chart filters. So typically a faint transparent color is better to use for this style, to bring focus to the highlighted series.
filtered: {
lineWidth: 1,
strokeStyle: 'rgba(0, 0, 0, 0.05)',
},
overrideNaN: StyleLine (optional)
The overrideNaN
style is in effect when a series has a NaN value.
overrideNaN: {
lineWidth: 1,
strokeStyle: 'rgba(255, 0, 0, 0.2)',
},
overrideNegativeInfinity: StyleLine (optional)
The overrideNegativeInfinity
style is in effect when a series has a -Infinity value.
overrideNegativeInfinity: {
lineWidth: 1,
strokeStyle: 'rgba(255, 0, 0, 0.2)',
},
overridePositiveInfinity: StyleLine (optional)
The overridePositiveInfinity
style is in effect when a series has a +Infinity value.
overridePositiveInfinity: {
lineWidth: 1,
strokeStyle: 'rgba(255, 0, 0, 0.2)',
},
path: PathOptions
The path
option provides control over how to render the series. Typically the PathType.Straight
is used to be able to pack more dimensions into the chart, but for large charts, PathType.Bezier
can be much more pleasing to visualize, which will render smooth and curving bezier curves.
path: {
options: {},
type: EPathType.Straight,
},
series: StyleLine[] (optional)
The series
is a list of styles that is used to provide finer control of how to draw each individual chart series. Each index of the series style maps to the series index in the data.
series: [
// Series 0 will be red.
{ lineWidth: 1, strokeStyle: 'rgba(255, 0, 0, 1.0)' },
// Series 1 will be green.
{ lineWidth: 1, strokeStyle: 'rgba(0, 255, 0, 1.0)' },
// Series 2 will be blue.
{ lineWidth: 1, strokeStyle: 'rgba(0, 0, 255, 1.0)' },
],
targetColorScale: string[] (optional)
The targetColorScale
is a list of colors (minimum of two) that determines the gradient that is used to draw the chart series, based on the target dimension (targetDimensionKey
).
targetDimensionKey: DimensionKey (optional)
The targetDimensionKey
is used in conjunction with targetColorScale
. This tells the chart which dimension to use to determine the color of the series based on that dimension value along the color scale range.
dimension
The dimension
options focus on the layout and styles of the dimensions as a collective. For modifying the axis portion of the dimensions, look at the axes options.
label: LabelMoveOptions
The label
options control where to draw the dimension labels relative to the dimension axes.
label: {
angle: undefined,
boundaryPadding: 5,
fillStyle: 'rgba(0, 0, 0, 1.0)',
font: 'normal 11px sans-serif',
lineWidth: 3,
offset: 16,
placement: ELabelPlacement.Before,
strokeStyle: 'rgba(255, 255, 255, 1.0)',
},
labelActive: StyleText
The labelActive
style is in effect when the user clicks on the dimension label to interative with the dimension.
labelActive: { fillStyle: 'rgba(99, 200, 255, 1.0)' },
labelHover: StyleText
The labelHover
style is in effect when the user hovers over the dimension label.
labelHover: { fillStyle: 'rgba(79, 180, 246, 1.0)' },
layout: DimensionLayout
The layout
option controls how the dimensions are spaced out.
DimensionLayout.AxisEvenlySpaced
draws the dimension axes even distances from each other. The dimension labels do not impact the layout.
DimensionLayout.Equidistant
draws the dimensions equidistant from each other. The overall width of the dimension counts towards calculations so dimension label and tick labels can impact the spacing.
padding: number | [ number, number ] | [ number, number, number, number ]
The padding
between the edge of the chart container and the chart content, such as the labels, axes and axis labels. The padding can be a single number, a list of two numbers or a list of 4 numbers.
// 8px on all four sides ([ 8, 8, 8, 8 ]).
padding: 8
// Padding of 16px on top and bottom and 8px on the left and right ([ 16, 8, 16, 8 ]).
padding: [ 16, 8 ]
// padding of 32px on top, 16px on the right, 8px on bottom, and 4px on the left.
padding: [ 32, 16, 8, 4 ]
Special Thanks
- Leon Sorokin's uPlot was a great source of inspiration and a lot of the setup work and deployment steps of Hermes are modeled after it. Leon has also provided some great guidance on some technical improvements.
- Alex Johnson provided some great feedback during development to improve the overall the user experience of Hermes.