Diverging Stacked Bar Chart

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Vega-Lite JSON Specification

{
  "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
  "description":
    "A diverging stacked bar chart for sentiments towards a set of eight questions, displayed as percentages with neutral responses straddling the 0% mark",
  "data": {
    "values": [
      {"question": "Question 1", "type": "Strongly disagree", "value": 24, "percentage": 0.7},
      {"question": "Question 1", "type": "Disagree", "value": 294, "percentage": 9.1},
      {"question": "Question 1", "type": "Neither agree nor disagree", "value": 594, "percentage": 18.5},
      {"question": "Question 1", "type": "Agree", "value": 1927, "percentage": 59.9},
      {"question": "Question 1", "type": "Strongly agree", "value": 376, "percentage": 11.7},
      {"question": "Question 2", "type": "Strongly disagree", "value": 2, "percentage": 18.2},
      {"question": "Question 2", "type": "Disagree", "value": 2, "percentage": 18.2},
      {"question": "Question 2", "type": "Neither agree nor disagree", "value": 0, "percentage": 0},
      {"question": "Question 2", "type": "Agree", "value": 7, "percentage": 63.6},
      {"question": "Question 2", "type": "Strongly agree", "value": 11, "percentage": 0},
      {"question": "Question 3", "type": "Strongly disagree", "value": 2, "percentage": 20},
      {"question": "Question 3", "type": "Disagree", "value": 0, "percentage": 0},
      {"question": "Question 3", "type": "Neither agree nor disagree", "value": 2, "percentage": 20},
      {"question": "Question 3", "type": "Agree", "value": 4, "percentage": 40},
      {"question": "Question 3", "type": "Strongly agree", "value": 2, "percentage": 20},
      {"question": "Question 4", "type": "Strongly disagree", "value": 0, "percentage": 0},
      {"question": "Question 4", "type": "Disagree", "value": 2, "percentage": 12.5},
      {"question": "Question 4", "type": "Neither agree nor disagree", "value": 1, "percentage": 6.3},
      {"question": "Question 4", "type": "Agree", "value": 7, "percentage": 43.8},
      {"question": "Question 4", "type": "Strongly agree", "value": 6, "percentage": 37.5},
      {"question": "Question 5", "type": "Strongly disagree", "value": 0, "percentage": 0},
      {"question": "Question 5", "type": "Disagree", "value": 1, "percentage": 4.2},
      {"question": "Question 5", "type": "Neither agree nor disagree", "value": 3, "percentage": 12.5},
      {"question": "Question 5", "type": "Agree", "value": 16, "percentage": 66.7},
      {"question": "Question 5", "type": "Strongly agree", "value": 4, "percentage": 16.7},
      {"question": "Question 6", "type": "Strongly disagree", "value": 1, "percentage": 6.3},
      {"question": "Question 6", "type": "Disagree", "value": 1, "percentage": 6.3},
      {"question": "Question 6", "type": "Neither agree nor disagree", "value": 2, "percentage": 12.5},
      {"question": "Question 6", "type": "Agree", "value": 9, "percentage": 56.3},
      {"question": "Question 6", "type": "Strongly agree", "value": 3, "percentage": 18.8},
      {"question": "Question 7", "type": "Strongly disagree", "value": 0, "percentage": 0},
      {"question": "Question 7", "type": "Disagree", "value": 0, "percentage": 0},
      {"question": "Question 7", "type": "Neither agree nor disagree", "value": 1, "percentage": 20},
      {"question": "Question 7", "type": "Agree", "value": 4, "percentage": 80},
      {"question": "Question 7", "type": "Strongly agree", "value": 0, "percentage": 0},
      {"question": "Question 8", "type": "Strongly disagree", "value": 0, "percentage": 0},
      {"question": "Question 8", "type": "Disagree", "value": 0, "percentage": 0},
      {"question": "Question 8", "type": "Neither agree nor disagree", "value": 0, "percentage": 0},
      {"question": "Question 8", "type": "Agree", "value": 0, "percentage": 0},
      {"question": "Question 8", "type": "Strongly agree", "value": 2, "percentage": 100}
    ]
  },
  "transform": [
    {"calculate":
        "if(datum.type === 'Strongly disagree',-2,0) + if(datum.type==='Disagree',-1,0) + if(datum.type =='Neither agree nor disagree',0,0) + if(datum.type ==='Agree',1,0) + if(datum.type ==='Strongly agree',2,0)",
      "as": "q_order"
    },
    {"calculate":
        "if(datum.type === 'Disagree' || datum.type === 'Strongly disagree', datum.percentage,0) + if(datum.type === 'Neither agree nor disagree', datum.percentage / 2,0)",
      "as": "signed_percentage"
    },
    {"stack": "percentage", "as": ["v1", "v2"], "groupby": ["question"]},
    {
      "window": [
        {
          "field": "signed_percentage",
          "op": "sum",
          "as": "offset"
        }
      ],
      "groupby": ["question"],
      "frame": [null, null]
    },
    {"calculate": "datum.v1 - datum.offset", "as": "nx"},
    {"calculate": "datum.v2 - datum.offset", "as": "nx2"}
  ],
  "mark": "bar",
  "encoding": {
    "x": {
      "field": "nx",
      "type": "quantitative",
      "axis": {
        "title": "Percentage"
      }
    },
    "x2": {"field": "nx2","type": "quantitative"},
    "y": {
      "field": "question",
      "type": "nominal",
      "axis": {
        "title": "Question",
        "offset": 5,
        "ticks": false,
        "minExtent": 60,
        "domain": false
      }
    },
    "color": {
      "field": "type",
      "type": "nominal",
      "legend": {
        "title": "Response"
      },
      "scale": {
        "domain": [
          "Strongly disagree",
          "Disagree",
          "Neither agree nor disagree",
          "Agree",
          "Strongly agree"
        ],
        "range": ["#c30d24", "#f3a583", "#cccccc", "#94c6da", "#1770ab"],
        "type": "ordinal"
      }
    }
  }
}