How can I add a year slider to this Ranged Dot Plot in Vega Lite? - json

Question

I have a dataset with relevant values from 2000-2019, and when I load up the graph with this specification:
"data": {
"name": "chart6",
"url": "https://raw.githubusercontent.com/sebaconstable/sebaconstable.github.io/main/chart6data.csv"
},
"height": 300,
"width": 450,
"encoding": {
"x": {
"field": "average years in school",
"type": "quantitative",
"scale": {"domain": [0, 20]},
"title": "Average Years in School"
},
"y": {
"field": "Country",
"type": "nominal",
"axis": {"offset": 5, "ticks": false, "minExtent": 70, "domain": false}
}
},
"layer": [
{
"mark": "line",
"encoding": {
"detail": {"field": "Country", "type": "nominal"},
"color": {"value": "#BBBBBB"}
}
},
{
"mark": {"type": "point", "filled": true},
"encoding": {
"tooltip": [
{"field": "Country", "type": "nominal", "title": "Country"},
{"field": "QuintGap", "type": "quantitative", "title": "Difference between richest and poorest quintile"},
{"field": "Median % Pop", "type": "nominal", "title": "Median % of population in CCT programmes (2000-2019)"}
],
"color": {
"field": "Quintile",
"type": "nominal",
"title": null,
"scale": {"scheme": "inferno"}
},
"size": {
"field": "Median % Pop",
"type": "quantitative",
"legend":null,
"scale": {"range": [10, 100]}
},
"opacity": {"value": 1}
}
}
]
}
The points for every year appear on each country. I want to make it so it has a year slider and then only the two points for the selected year show.
I have tried many things. I added:
"transform": [
{"filter": {"field": "Quintile", "oneOf": ["Poorest Quintile", "Richest Quintile"]}},
{"filter": "datum.Year==selecta"}
],
"params": [
{
"name": "selecta",
"value": [{"year":2019}],
"bind": {
"input": "range",
"min": 2000,
"max": 2019,
"step": 1,
"name": "Select year:"
}
}
],
this code above the first encoding, and that successfully creates a slider (which filters to the relevant data correctly) however the rest of the chart disappears. I also tried adding a filter to "oneOf" the 20 years, however this made the visualisation dissapear.
I feel that I'm quite close to the solution but after several hours can't quite figure it out. Any help is much appreciated!

Answer 1

Here you go.
{
"data": {
"name": "chart6",
"url": "https://raw.githubusercontent.com/sebaconstable/sebaconstable.github.io/main/chart6data.csv"
},
"transform": [{"filter": "datum.Year==selecta"}],
"params": [
{
"name": "selecta",
"value": [2019],
"bind": {
"input": "range",
"min": 2000,
"max": 2019,
"step": 1,
"name": "Select year:"
}
}
],
"height": 300,
"width": 450,
"encoding": {
"x": {
"field": "average years in school",
"type": "quantitative",
"scale": {"domain": [0, 20]},
"title": "Average Years in School"
},
"y": {
"field": "Country",
"type": "nominal",
"axis": {"offset": 5, "ticks": false, "minExtent": 70, "domain": false}
}
},
"layer": [
{
"mark": "line",
"encoding": {
"detail": {"field": "Country", "type": "nominal"},
"color": {"value": "#BBBBBB"}
}
},
{
"mark": {"type": "point", "filled": true},
"encoding": {
"tooltip": [
{"field": "Country", "type": "nominal", "title": "Country"},
{
"field": "QuintGap",
"type": "quantitative",
"title": "Difference between richest and poorest quintile"
},
{
"field": "Median % Pop",
"type": "nominal",
"title": "Median % of population in CCT programmes (2000-2019)"
}
],
"color": {
"field": "Quintile",
"type": "nominal",
"title": null,
"scale": {"scheme": "inferno"}
},
"size": {
"field": "Median % Pop",
"type": "quantitative",
"legend": null,
"scale": {"range": [10, 100]}
},
"opacity": {"value": 1}
}
}
]
}