vega - Vega embed 不渲染图

Question

我正在尝试重现本教程 https://nyurik.github.io/Vega-Trends-Graph-for-Kibana/

虽然 spec 在 kibana-vega 插件（kibana 版本 6.3.0）中呈现，但完全相同的 sepc 不会在 vega 在线编辑器中呈现任何可视化。vega embed 没有引发任何错误，并且数据查看器看起来数据已正确处理。
vega 嵌入带有规范的在线编辑器

{
  "$schema": "https://vega.github.io/schema/vega/v3.0.json",
  "data": [
    {
      "name": "values",
      "values" : [{"key_as_string":"2018-08-15T16:22:00.000Z","key":1534350120000,"doc_count":0},{"key_as_string":"2018-08-15T16:23:00.000Z","key":1534350180000,"doc_count":3},{"key_as_string":"2018-08-15T16:24:00.000Z","key":1534350240000,"doc_count":11},{"key_as_string":"2018-08-15T16:25:00.000Z","key":1534350300000,"doc_count":9},{"key_as_string":"2018-08-15T16:26:00.000Z","key":1534350360000,"doc_count":10},{"key_as_string":"2018-08-15T16:27:00.000Z","key":1534350420000,"doc_count":8},{"key_as_string":"2018-08-15T16:28:00.000Z","key":1534350480000,"doc_count":5},{"key_as_string":"2018-08-15T16:29:00.000Z","key":1534350540000,"doc_count":4},{"key_as_string":"2018-08-15T16:30:00.000Z","key":1534350600000,"doc_count":7},{"key_as_string":"2018-08-15T16:31:00.000Z","key":1534350660000,"doc_count":8},{"key_as_string":"2018-08-15T16:32:00.000Z","key":1534350720000,"doc_count":11},{"key_as_string":"2018-08-15T16:33:00.000Z","key":1534350780000,"doc_count":6},{"key_as_string":"2018-08-15T16:34:00.000Z","key":1534350840000,"doc_count":6},{"key_as_string":"2018-08-15T16:35:00.000Z","key":1534350900000,"doc_count":8},{"key_as_string":"2018-08-15T16:36:00.000Z","key":1534350960000,"doc_count":4},{"key_as_string":"2018-08-15T16:37:00.000Z","key":1534351020000,"doc_count":12},{"key_as_string":"2018-08-15T16:38:00.000Z","key":1534351080000,"doc_count":8},{"key_as_string":"2018-08-15T16:39:00.000Z","key":1534351140000,"doc_count":8},{"key_as_string":"2018-08-15T16:40:00.000Z","key":1534351200000,"doc_count":7},{"key_as_string":"2018-08-15T16:41:00.000Z","key":1534351260000,"doc_count":9}],
      "transform": [
        {
          "type": "window",
          "ops": [
            "row_number"
          ],
          "as": [
            "row_number"
          ]
        },
        {
          "type": "formula",
          "expr": "floor((datum.row_number-1)/10)",
          "as": "group"
        },
        {
          "type": "aggregate",
          "groupby": [
            "group"
          ],
          "ops": [
            "sum"
          ],
          "fields": [
            "doc_count"
          ],
          "as": [
            "count"
          ]
        }
      ]
    },
    {
      "name": "results",
      "values": [
        {}
      ],
      "transform": [
        {
          "type": "formula",
          "expr": "data('values')[0].count",
          "as": "last"
        },
        {
          "type": "formula",
          "expr": "data('values')[1].count",
          "as": "prev"
        },
        {
          "type": "formula",
          "expr": "datum.last>datum.prev",
          "as": "up"
        },
        {
          "type": "formula",
          "expr": "datum.last<datum.prev",
          "as": "down"
        },
        {
          "type": "formula",
          "expr": "if(datum.last==0, if(datum.prev==0,0,-1), (datum.last-datum.prev)/datum.last)",
          "as": "percentChange"
        },
        {
          "type": "formula",
          "expr": "if(datum.up,':)',if(datum.down,':(','-'))",
          "as": "symbol"
        }
      ]
    }
  ],
  "marks": [
    {
      "type": "text",
      "from": {
        "data": "results"
      },
      "encode": {
        "update": {
          "text": {
            "signal": "datum.symbol + ' ' + datum.last + ' ('+ format(datum.percentChange, '+.1%') + ')'"
          },
          "fill": {
            "signal": "if(datum.up, '#00ff00', if(datum.down, '#ff0000', '#0000ff'))"
          },
          "align": {
            "value": "center"
          },
          "baseline": {
            "value": "middle"
          },
          "xc": {
            "signal": "width/2"
          },
          "yc": {
            "signal": "height/2"
          },
          "fontSize": {
            "signal": "min(width/10, height)/1.3"
          }
        }
      }
    }
  ]
}