Executive Orders by presidential term

spec.json

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "data": { "url": "https://www.federalregister.gov/api/v1/documents.json?conditions%5Bcorrection%5D=0&conditions%5Bpresidential_document_type%5D=executive_order&conditions%5Btype%5D%5B%5D=PRESDOCU&fields%5B%5D=citation&fields%5B%5D=document_number&fields%5B%5D=president&fields%5B%5D=type&fields%5B%5D=subtype&fields%5B%5D=publication_date&fields%5B%5D=signing_date&fields%5B%5D=title&fields%5B%5D=effective_on&fields%5B%5D=executive_order_number&per_page=1200", "format": { "type": "json", "property": "results"}},
  "transform": [  
    { "filter": "year(datum.publication_date) > 1996"},
      {
        "joinaggregate": [{
          "op": "min",
          "field": "publication_date",
          "as": "firstYear"
        }],
        "groupby": [
          "president.name"
        ]
      },
      {
        "calculate": "year(datum.publication_date)-year(datum.firstYear) + 1", 
        "as": "yearInOffice"
      },
      {
        "calculate": "ceil(datum.yearInOffice/4) + (month(datum.publication_date) == 0 && datum.yearInOffice > 4 ? -1 : 0)", 
        "as": "term"
      },
      {
        "calculate": "((datum.term - 1) * 4) + year(datum.firstYear)", 
        "as": "firstYearInTerm"
      },
      {
        "calculate": "datum.president.name + ' (' + datum.firstYearInTerm + '-' + (datum.firstYearInTerm + 3) + ')'", 
        "as": "president_term"
      }],
  "width": {"step": 20},
  "mark": "bar",
  "encoding": {
    "x": {
      "aggregate": "count", "field": "subtype",
      "title": "executive orders published",
      "axis": {"grid": false}
    },
    "y": {
      "sort": {"field": "firstYear"},
      "field": "president_term",
      "axis": {"title": ""}
    },
    "color": {
      "field": "president.name",
      "title": ""
    }
  },
  "config": {
    "view": {"stroke": "transparent"},
    "axis": {"domainWidth": 1}
  }
}