Sort bars of Stacked Bar Chart - vega-lite

Question

For a Stacked Bar Chart, can you sort the bars by the size of one of the segments?
E.g., take this Stacked Bar Chart from the examples (Open Editor):
{
"$schema": "https://vega.github.io/schema/vega-lite/v5.json",
"data": {"url": "data/barley.json"},
"mark": "bar",
"encoding": {
"x": {"aggregate": "sum", "field": "yield"},
"y": {"field": "variety"},
"color": {"field": "site"}
}
}
Now I would like to sort the y-axis based on the yield in Crookston. Is that possible?

Answer 1

Sorting by the total of another field is relatively easy; you can do so with the "sort" entry of the desired encoding (sort docs):
{
"$schema": "https://vega.github.io/schema/vega-lite/v5.json",
"data": {"url": "data/barley.json"},
"mark": "bar",
"encoding": {
"x": {"aggregate": "sum", "field": "yield"},
"y": {"field": "variety", "sort": {"op": "sum", "field": "yield"}},
"color": {"field": "site"}
}
}
If you want to sort just by the value when site == "Crookston", you can do so by first applying a calculate transform to select just that value:
{
"$schema": "https://vega.github.io/schema/vega-lite/v5.json",
"data": {"url": "data/barley.json"},
"transform": [
{
"calculate": "datum.site == 'Crookston' ? datum.yield : 0",
"as": "crookston"
}
],
"mark": "bar",
"encoding": {
"x": {"aggregate": "sum", "field": "yield"},
"y": {"field": "variety", "sort": {"op": "sum", "field": "crookston"}},
"color": {"field": "site"}
}
}