Bar Graph Not Showing Up Using Vega

[Ethan777100 (Ethan Chia)]

Need help with Vega, my bar graph is not showing and i dont get why.

Whilst on the job,

I plan to manipulate "Align_Distance_To_Go_mm" to extract the counts of the number of its values within +/-300 and assign it to a new variable.

After which, i want to extract the global count of this "Align_Distance_To_Go_mm" and do a calculate to find the percentage of values within +/-300 classified by "Current_Platform_Name"

Pls help me see if my code can improve. Thanks

    {
      "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
      "data": {
        "url": {
          "%context%": true,
          "%timefield%": "DateTime",
          "index": "nsew*",
          "body": {
            "size": 10000,
            "_source": [
              "Current_Platform_Name",
              "Align_Distance_To_Go_mm",
              "Train_Type"
            ]
          }
        },
        "format": {"property": "hits.hits"}
      },
      "transform": [
        {
          "filter": {
            "field": "datum._source['Align_Distance_To_Go_mm']",
            "range": [-300, 300]
          }
        },
        {
          "joinaggregate": [
            {
              "op": "count",
              "field": "datum.Align_Distance_To_Go_mm",
              "as": "count_all_Dist"
            }
          ],
          "groupby": ["Current_Platform_Name"]
        },
        {
          "joinaggregate": [
            {
              "op": "count",
              "field": "datum.Align_Distance_To_Go_mm",
              "as": "count_within_Dist"
            }
          ],
          "groupby": ["Current_Platform_Name"]
        },
        {
          "calculate": " (datum.count_within_Dist/datum.count_all_Dist)*100 ",
          "as": "Percent_Compliance"
        }
      ],
      "layer": [
        {
          "mark": "bar",
          "height": {"step": 5},
          "encoding": {
            "x": {
              "field": "Percent_Compliance",
              "type": "quantitative",
              "axis": {"title": "Percent_Compliance"}
            },
            "y": {
              "field": "_source.Current_Platform_Name",
              "type": "nominal",
              "axis": {"title": "Platform Name"}
            },
            "color": {
              "field": "_source.Current_Platform_Name",
              "type": "nominal",
              "legend": {"title": "Platform Legend"}
            },
            "shape": {"field": "_source.Current_Platform_Name", "type": "nominal"}
          }
        }
      ]
    }