Waterfall Chart of Monthly Profit and Loss

{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "data": {
    "values": [
      {"label": "Begin", "amount": 4000},
      {"label": "Jan", "amount": 1707},
      {"label": "Feb", "amount": -1425},
      {"label": "Mar", "amount": -1030},
      {"label": "Apr", "amount": 1812},
      {"label": "May", "amount": -1067},
      {"label": "Jun", "amount": -1481},
      {"label": "Jul", "amount": 1228},
      {"label": "Aug", "amount": 1176},
      {"label": "Sep", "amount": 1146},
      {"label": "Oct", "amount": 1205},
      {"label": "Nov", "amount": -1388},
      {"label": "Dec", "amount": 1492},
      {"label": "End", "amount": 0}
    ]
  },
  "width": 800,
  "height": 450,
  "transform": [
    {"window": [{"op": "sum", "field": "amount", "as": "sum"}]},
    {"window": [{"op": "lead", "field": "label", "as": "lead"}]},
    {
      "calculate": "datum.lead === null ? datum.label : datum.lead",
      "as": "lead"
    },
    {
      "calculate": "datum.label === 'End' ? 0 : datum.sum - datum.amount",
      "as": "previous_sum"
    },
    {
      "calculate": "datum.label === 'End' ? datum.sum : datum.amount",
      "as": "amount"
    },
    {
      "calculate": "(datum.label !== 'Begin' && datum.label !== 'End' && datum.amount > 0 ? '+' : '') + datum.amount",
      "as": "text_amount"
    },
    {"calculate": "(datum.sum + datum.previous_sum) / 2", "as": "center"},
    {
      "calculate": "datum.sum < datum.previous_sum ? datum.sum : ''",
      "as": "sum_dec"
    },
    {
      "calculate": "datum.sum > datum.previous_sum ? datum.sum : ''",
      "as": "sum_inc"
    }
  ],
  "encoding": {
    "x": {"field": "label", "type": "ordinal", "sort": null, "title": "Months"}
  },
  "layer": [
    {
      "mark": {"type": "bar", "size": 45},
      "encoding": {
        "y": {
          "field": "previous_sum",
          "type": "quantitative",
          "title": "Amount"
        },
        "y2": {"field": "sum", "type": "quantitative"},
        "color": {
          "condition": [
            {
              "test": "datum.label === 'Begin' || datum.label === 'End'",
              "value": "#f7e0b6"
            },
            {"test": "datum.sum < datum.previous_sum", "value": "#f78a64"}
          ],
          "value": "#93c4aa"
        }
      }
    },
    {
      "mark": {
        "type": "rule",
        "color": "#404040",
        "opacity": 1,
        "strokeWidth": 2,
        "xOffset": -22.5,
        "x2Offset": 22.5
      },
      "encoding": {
        "x2": {"field": "lead", "type": "ordinal"},
        "y": {"field": "sum", "type": "quantitative"}
      }
    },
    {
      "mark": {
        "type": "text",
        "dy": -8,
        "fontWeight": "bold",
        "color": "#404040"
      },
      "encoding": {
        "y": {"field": "sum_inc", "type": "quantitative"},
        "text": {"field": "sum_inc", "type": "nominal"}
      }
    },
    {
      "mark": {
        "type": "text",
        "dy": 8,
        "baseline": "top",
        "fontWeight": "bold",
        "color": "#404040"
      },
      "encoding": {
        "y": {"field": "sum_dec", "type": "quantitative"},
        "text": {"field": "sum_dec", "type": "nominal"}
      }
    },
    {
      "mark": {"type": "text", "fontWeight": "bold", "baseline": "middle"},
      "encoding": {
        "y": {"field": "center", "type": "quantitative"},
        "text": {"field": "text_amount", "type": "nominal"},
        "color": {
          "condition": [
            {
              "test": "datum.label === 'Begin' || datum.label === 'End'",
              "value": "#725a30"
            }
          ],
          "value": "white"
        }
      }
    }
  ]
}