This is an example dataset to demonstrate how data transforms work. In this example, we explain how to aggregate a resource. We assume a publisher is already familiar with Data Packages and views specifications (views property in Data Package specifications).

Transforming data

Data transforms are specified in resources attribute of views property. Each resource is an object that contains following attributes:

• "name" - name of the resource as a reference.
• "transform" - array of transforms. Each transform is an object, which properties vary depending on transform type.

Aggregating data

Under the graph on the top of this page, you can find a table that displays aggregated data. Raw data is displayed in preview section. As you can see we are aggregating "GDP" column to find its min value and "GDP_Change" column for max value. This is described in the second view object of views property:

{
  "name": "table-view-aggregation",
  "specType": "table",
  "resources": [
    {
      "name": "annual",
      "transform": [
        {
          "type": "aggregate",
          "fields": ["GDP", "GDP_Change"],
          "operations": ["min", "max"]
        }
      ]
    }
  ]
}

where in transform property:

• "type": "aggregate" - this way we define the transform to be an aggregation.
• "fields" - list of fields for which data aggregation will be applied.
• "operations" - list of operation names according to list of fields. Options are: "sum", "min", "max", "count", etc. For full reference see https://vega.github.io/vega/docs/transforms/aggregate/#ops .

Descriptor for this data package

This is the full datapackage.json of this dataset:

{
  "licenses": [
    {
      "id": "odc-pddl",
      "url": "http://opendatacommons.org/licenses/pddl/"
    }
  ],
  "name": "transform-example-gdp-uk",
  "resources": [
    {
      "name": "annual",
      "path": "annual.csv",
      "schema": {
        "fields": [
          {
            "format": "any",
            "name": "Year",
            "type": "date"
          },
          {
            "description": "Gross Value Added at basic prices: chained volume measures: Seasonally adjusted. Millions of GBP in base period money. Base period=2009. ABMI variable in ONS source.",
            "name": "GDP",
            "type": "number"
          },
          {
            "description": "Gross Domestic Product: Year on Year growth: CVM SA. IHYP variable in ONS source.",
            "format": "percentage",
            "name": "GDP_Change",
            "type": "number"
          },
          {
            "description": "Gross domestic product index. Base period=2009. YBEZ variable in ONS source.",
            "name": "GDP_Index",
            "type": "number"
          }
        ]
      },
      "sources": [
        {
          "web": "http://www.ons.gov.uk/ons/datasets-and-tables/data-selector.html?cdid=ABMI&dataset=qna&table-id=C2"
        }
      ]
    }
  ],
  "sources": [
    {
      "homepage": "http://www.ons.gov.uk/ons/rel/gva/gross-domestic-product--preliminary-estimate/q4-2012/tsd---preliminary-estimate-of-gdp-q4-2012.html",
      "name": "Office for National Statistics - GDP Time Series",
      "web": "http://www.ons.gov.uk/ons/datasets-and-tables/downloads/csv.csv?dataset=pgdp"
    }
  ],
  "title": "Example Aggregation on UK Gross Domestic Product (GDP)",
  "views": [
    {
      "id": "Graph",
      "state": {
        "graphType": "columns",
        "group": "Year",
        "series": [
          "GDP_Change"
        ]
      },
      "type": "Graph"
    },
    {
      "name": "table-view-aggregation",
      "specType": "table",
      "resources": [
        {
          "name": "annual",
          "transform": [
            {
              "type": "aggregate",
              "fields": ["GDP", "GDP_Change"],
              "operations": ["min", "max"]
            }
          ]
        }
      ]
    }
  ]
}