Deneb/Vega-Lite can be used to create dynamic timelines to animate data. While there is no direct method to animate data in Vega-Lite, the timer event from the Vega language can be used in Vega-Lite and leveraged and to generate a dynamic filter value.
The example presented herein shows an animation of the historical volcanic eruptions with 3 pages with differing start years (0, 1000, 2000; the Deneb/Vega-Lite code is identical for each page and differs only in the 1 line designating the start year). Historical eruption data was obtained from the Global Volcanism Program of the Smithsonian Institution, National Museum of Natural History.
This example illustrates a number of Deneb/Vega-Lite features, including:
0 - General:
- a “title” block with subtitle array
- a shared “params” block with:
- 2x named parameters for map fill and stroke colours (light grey, medium grey)
- a “timer” event set to fire at 500 millisecond intervals to recalculate the current time
- 2x named (fixed) parameters for the start time and start year
- a shared “transform” block with:
- a “calculate” transform to determine the specific decade (using the current time, the start time, and the start year parameters)
- a “filter” transform to restrict the dataset to a specific decade
- a vertical concatenation (vconcat) block for the eruptions and timeline
1 - Eruptions:
- a “layer” block with:
- a world map block with a hard-coded dataset with:
- the “mercator” projection within Vega-Lite
- a “geoshape” mark
- a nested “layer” block for the eruptions with:
- a “point” mark for the volcano location with size, colour, and shape conditional on the volcanic explosivity index (VEI)
- a “text” mark for the volcano name (filtered to only a few select volcanos for illustrative purposes)
- a world map block with a hard-coded dataset with:
2 - Timeline:
- a nested “transform” block with:
- a “window/rank” transform to identify the minimum row for the specific decade
- a “filter” transform to restrict the dataset to the single minimum row only
- a “calculate” transform to compose the decade data label
- a nested “layer” block with:
- a “point/triangle-down” mark for the decade pointer
- a “text” mark for the decade label
NOTE: the hard-coded map data comprised the vast majority of the JSON code (>99.3%) with the marks and encoding taking less than 280 formatted lines (<0.7% of the total).
Deneb/Vega-Lite JSON Code:
{
"title": {
"anchor": "start",
"align": "left",
"offset": 10,
"text": "Power BI Dynamic Timelines using Deneb/Vega-Lite",
"font": "Segoe UI",
"fontSize": 32,
"fontWeight": "bold",
"fontStyle": "normal",
"subtitle": [
"World Volcanic Eruptions by Decade",
"(names shown only for select volcanos for illustrative purposes)",
"Data Source: Smithsonian Institution, National Museum of Natural History, Global Volcanism Program, https://volcano.si.edu/database/search_eruption_results.cfm"
],
"subtitleFont": "Segoe UI",
"subtitleFontSize": 18,
"subtitleFontWeight": "normal",
"subtitleFontStyle": "italic"
},
"autosize": {
"resize": true
},
"padding": {
"left": 10,
"top": 5,
"right": 5,
"bottom": 5
},
"data": {
"name": "dataset"
},
"params": [
{
"name": "_colour_map_fill",
"value": "#E3E3E3"
},
{
"name": "_colour_map_stroke",
"value": "#B0B0B0"
},
{
"name": "_current_time",
"on": [
{
"events": {
"type": "timer",
"throttle": 500
},
"update": "now()"
}
]
},
{
"name": "_start_time",
"expr": "now()"
},
{
"name": "_start_year",
"value": 0
}
],
"transform": [
{
"calculate": "_current_time - _start_time",
"as": "_elapsed_time"
},
{
"calculate": "_start_year + floor( datum['_elapsed_time'] / 1000 ) * 10",
"as": "_decade"
},
{
"calculate": "if( datum['_decade'] > 2020, 2020, datum['_decade'] )",
"as": "_decade"
},
{
"filter": "datum['Decade'] == datum['_decade']"
}
],
"spacing": 10,
"vconcat": [
{
"name": "WORLD",
"width": 1650,
"height": 1150,
"layer": [
{
"name": "MAP",
"data": {
... // data removed for clarity
},
"mark": {
"type": "geoshape",
"fill": {
"expr": "_colour_map_fill"
},
"stroke": {
"expr": "_colour_map_stroke"
}
}
},
{
"name": "VOLCANOS",
"layer": [
{
"name": "VOLCANO_POINT",
"transform": [
{
"calculate": "datum['VEI']",
"as": "_explosivity_index"
}
],
"mark": {
"type": "point",
"filled": true,
// "color": "#0F4C81",
"opacity": 0.7,
"tooltip": true
},
"encoding": {
"latitude": {
"field": "Latitude",
"type": "quantitative"
},
"longitude": {
"field": "Longitude",
"type": "quantitative"
},
"size": {
"field": "_explosivity_index",
"type": "quantitative",
"legend": {
"title": [
"Volcanic",
"Explosivity",
"Index"
],
"titleFont": "Segoe UI",
"titleFontSize": 14
}
},
"color": {
"field": "_explosivity_index",
"type": "quantitative"
},
"shape": {
"field": "_explosivity_index",
"type": "nominal",
"legend": {
"title": null,
"symbolSize": 800
}
}
}
},
{
"name": "VOLCANO_TEXT",
"transform": [
{
"filter": "datum['Notable'] == 1"
}
],
"mark": {
"type": "text",
"align": "left",
"dy": 20,
"font": "Segoe UI",
"fontSize": 12,
"fontWeight": "normal",
"fontStyle": "italic",
"color": "black"
},
"encoding": {
"latitude": {
"field": "Latitude",
"type": "quantitative"
},
"longitude": {
"field": "Longitude",
"type": "quantitative"
},
"text": {
"field": "Volcano Name",
"type": "nominal"
}
}
}
]
}
]
},
{
"name": "TIMELINE",
"width": 1650,
"height": 10,
"transform": [
{
"window": [
{
"op": "rank",
"as": "_row_rank"
}
],
"sort": [
{
"field": "__row__",
"order": "descending"
}
]
},
{
"filter": "datum['_row_rank'] == 1"
},
{
"calculate": "datum['Decade'] + 's'",
"as": "_decade_label"
}
],
"layer": [
{
"name": "DECADE_POINTER",
"mark": {
"type": "point",
"shape": "triangle-down",
"filled": true,
"size": 400,
"color": "black"
},
"encoding": {
"y": {
"datum": 1,
"axis": null
},
"x": {
"field": "Decade",
"type": "quantitative",
"axis": {
"format": ".0f",
"labelFlush": true,
"title": null
},
"scale": {
"domain": [
0,
2060
]
}
}
}
},
{
"name": "DECADE_LABEL",
"mark": {
"type": "text",
"align": "left",
"xOffset": 20,
"font": "Segoe UI",
"fontWeight": "lighter",
"fontSize": 18
},
"encoding": {
"text": {
"field": "_decade_label"
},
"y": {
"datum": 1,
"axis": null
},
"x": {
"field": "Decade",
"type": "quantitative",
"axis": {
"format": ".0f",
"labelFont": "Segoe UI",
"labelFontSize": 12
}
}
}
]
}
]
}
Also included is the development sample PBIX using, as noted above, the historical eruption data from the Global Volcanism Program of the Smithsonian Institution, National Museum of Natural History.
The intent of this example was not to provide a finished visual, but rather to explore the use of the Deneb custom visual and the Vega-Lite language within Power BI and to serve as a starting point for further development.
This example is provided as-is for information purposes only, and its use is solely at the discretion of the end user; no responsibility is assumed by the author.
Greg
Deneb Example - Dynamic Timelines - V5.pbix (3.3 MB)