{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "name": "ExpenseCategories",
  "title": {
    "text": "Expense breakdown",
    "subtitle": "Amount per week ($)"
  },
  "data": { "url": "../charts/expensecategories.csv"},

  "transform": [
    { "calculate": "split(datum.account, ':', 2)", "as": "accountpair" },
    {
      "window": [{"op": "mean", "field": "value", "as": "rolling_mean"}],
      "groupby": ["accountpair"],
      "frame": [-13, 0]
    },
    { "calculate": "datum.rolling_mean * 7", "as": "weekly" }
  ],

  "facet": {
    "field": "accountpair.0",
    "type": "ordinal",
    "sort": { "op": "sum", "field": "weekly", "order": "descending" },
    "legend": { "title": null }
  },

  "columns": 2,
  "resolve": { "scale": { "y": "independent", "color": "independent" } },

  "params": [{
    "name": "grid",
    "select": "interval",
    "bind": "scales"
  }],

  "spec": {
    "width": 750,
    "height": 190,

    "mark": "line",
    "encoding": {
      "x": {
        "field": "end_date",
        "title": null,
        "type": "temporal",
        "scale": { "domainMin": { "expr": "timeOffset('year', now(), -1)" } }
      },
      "y": {
        "field": "weekly",
        "title": null,
        "type": "quantitative",
        "stack": true
      },
      "color": {
        "field": "accountpair.1",
        "type": "nominal",
        "legend": { "title": null }
      }
    }
  }
}