如何向 vega 条形图列添加最小像素高度

Question

我在 Vega 中制作了一个条形图，每个类别有两列。有谁知道如何设置每列的最小像素高度？

当值不等于 0 时，我希望它的最小像素高度为 2px，因为有时数据会发生变化，并且您只能看到很少的值，具体取决于它在范围上的渲染方式。

这是我当前的实现：

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "width": 700,
  "height": 370,
  "autosize": {"type": "fit", "contains": "padding"},
  "padding": {"bottom": 2, "right": 9, "left": 5},
  "config": {
    "axis": {
      "labelFont": "HelveticaNeueLTW01-55Roman",
      "titleFont": "HelveticaNeueLTW01-55Roman"
    }
  },
  "data": [
    {
      "name": "capital_flows",
      "values": [
        {"label": "2012", "value1": 90.75, "value2": 114.11},
        {"label": "2013", "value1": 17.36, "value2": -17.54},
        {"label": "2014", "value1": 7.36, "value2": -100.43},
        {"label": "2015", "value1": 8.64, "value2": -0.07},
        {"label": "2016", "value1": 3.36, "value2": -1.01},
        {"label": "2017", "value1": 10.48, "value2": -1.29},
        {"label": "2018", "value1": 6.32, "value2": -84.2},
        {"label": "2019", "value1": 3.29, "value2": -3.06}
      ],
      "transform": [
        {"type": "formula", "expr": "split(datum.label, ' ')", "as": "label"}
      ]
    },
    {
      "name": "parsed",
      "source": ["capital_flows"],
      "transform": [
        {
          "type": "aggregate",
          "fields": ["value1", "value1", "value2", "value2"],
          "ops": ["min", "max", "min", "max"],
          "as": ["min_value1", "max_value1", "min_value2", "max_value2"]
        },
        {
          "type": "formula",
          "expr": "datum.min_value1 && datum.min_value2 == 0 ? 1 : datum.max_value1 > datum.max_value2 ? abs(datum.max_value1) : abs(datum.max_value2)",
          "as": "mergedMax"
        },
        {
          "type": "formula",
          "expr": "datum.min_value1 && datum.min_value2 == 0 ? 1 : datum.min_value1 < datum.min_value2 ? abs(datum.min_value1) : abs(datum.min_value2)",
          "as": "mergedMin"
        },
        {
          "type": "formula",
          "expr": "datum.mergedMax > datum.mergedMin ? datum.mergedMax : datum.mergedMin",
          "as": "max"
        },
        {"type": "formula", "expr": "-(datum.max)", "as": "min"}
      ]
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "band",
      "range": "width",
      "domain": {"data": "capital_flows", "field": "label"}
    },
    {
      "name": "y",
      "type": "linear",
      "range": "height",
      "nice": true,
      "zero": false,
      "domain": {"data": "parsed", "field": "limit"},
      "domainMin": {"signal": "pluck(data('parsed'), 'min')"},
      "domainMax": {"signal": "pluck(data('parsed'), 'max')"}
    }
  ],
  "axes": [
    {
      "orient": "bottom",
      "scale": "x",
      "zindex": 1,
      "labelFontSize": 14,
      "labelColor": "#85868C",
      "labelAlign": "center",
      "labelLineHeight": 19.6,
      "labelFontWeight": "normal",
      "labelPadding": 8,
      "labelOpacity": 1,
      "domain": false,
      "domainColor": "#e5e5e5",
      "domainWidth": 1,
      "ticks": false
    },
    {
      "orient": "left",
      "scale": "y",
      "zindex": 0,
      "labelFontSize": 14,
      "labelColor": "#85868C",
      "labelLineHeight": 19.6,
      "labelFontWeight": "normal",
      "labelPadding": 8,
      "labelOpacity": 1,
      "domain": false,
      "domainColor": "#e5e5e5",
      "grid": true,
      "gridOpacity": 0.5,
      "ticks": false,
      "tickCount": 4,
      "gridDash": {"signal": "datum.value == 0 ? [] : [4,4]"},
      "encode": {
        "labels": {
          "update": {
            "text": {
              "signal": "if(abs(datum.value) >= 1e9, format(datum.value/1e9, '$,.1~f') + 'B', if(abs(datum.value) >= 1e6, format(datum.value/1e6, '$,.1~f') + 'M', if(abs(datum.value) >= 1e3, format(datum.value/1e3, '$,.1~f') + 'K', format(datum.value, '$,.2~f'))))"
            }
          }
        }
      }
    }
  ],
  "marks": [
    {
      "name": "inflow",
      "type": "rect",
      "from": {"data": "capital_flows"},
      "encode": {
        "enter": {
          "xc": {"scale": "x", "field": "label", "band": 0.5},
          "width": {"value": 16},
          "y": {"scale": "y", "field": "value1"},
          "y2": {"scale": "y", "value": 0},
          "fill": {"value": "#68c487"},
          "cornerRadiusTopLeft": {"signal": "datum.value1 > 0 ? '2' : '0'"},
          "cornerRadiusTopRight": {"signal": "datum.value1 > 0 ? '2' : '0'"},
          "cornerRadiusBottomLeft": {"signal": "datum.value1 > 0 ? '0' : '2'"},
          "cornerRadiusBottomRight": {"signal": "datum.value1 > 0 ? '0' : '2'"}
        }
      }
    },
    {
      "name": "outflow",
      "type": "rect",
      "from": {"data": "capital_flows"},
      "encode": {
        "enter": {
          "xc": {"scale": "x", "field": "label", "band": 0.5, "offset": 18},
          "width": {"value": 16},
          "y": {"scale": "y", "field": "value2"},
          "y2": {"scale": "y", "value": 0},
          "fill": {"value": "#FFB066"},
          "cornerRadiusTopLeft": {"signal": "datum.value2 > 0 ? '2' : '0'"},
          "cornerRadiusTopRight": {"signal": "datum.value2 > 0 ? '2' : '0'"},
          "cornerRadiusBottomLeft": {"signal": "datum.value2 > 0 ? '0' : '2'"},
          "cornerRadiusBottomRight": {"signal": "datum.value2 > 0 ? '0' : '2'"}
        }
      }
    }
  ]
}

Answer 1

您可以添加一个额外的转换，如下所示：

{"type": "formula", "expr": "datum.value2 < 0 && datum.value2 > -1 ? -1: datum.value2 > 0 && datum.value2 < 1 ? 1: datum.value2", "as": "value2"}

所以：

如果它在 -1 和 0 之间，那么它将是 -1

如果介于 0 和 1 之间，则为 1

还要在图表底部添加注释，因为它可能会产生误导:)