schema

Schema

Schema is used to describe a field present in data. Schema definition is a simple key value pair.

Following properties are available on the schema object both for measure and dimension.

Property	Description	Required	Example
name	Name of the field	true	"sales"
type	Type of field (dimension or measure)	false (defaults to "dimenson"	"dimension"
subtype	Subtype of field	false	"Temporal"
defAggFn	Default aggregation function for measures	false	"sum"
format	Format specification for dates/numbers	false	"MM/DD/YYYY"
displayName	Custom name for field display	false	"Total Sales"

1. name: Name of the variable.

• The field must exist in the data. It is the only mandatory property in schema.

2. type: type of the variable.

• The options are 'measure' and 'dimension'. Default is 'dimension'.

For a dimension the following fields are available on schema object

• subtype: specifies what kind of dimension it is.
  • Currently the options are 'categorical', 'temporal' and 'binned'.
  • Default is 'categorical'
• format: This filed has a multi usage as described below
  • If subtype temporal and the value type of data of this field is in timestamp then it can have function which will be used to get the value from datamodel in that format.
  • If subtype temporal and the value type of data of this field is in string format , then this should have the format of Date data which will be used to parse the date.
  • If subtype is categorical , this should have a function to format the data in this field.
• binSize: This should be of type Number to provide bin size for binned field.

For a measure the following fields are available on schema object

• subtype: The subtype for measure is always is 'continuous'
• defAggFn: function to be used when field is aggregated.
• format: a function which returns the formatted value of a variable. This is only for output purpose.

Name	Miles_per_Gallon	Cylinders	Displacement	Horsepower	Weight_in_lbs	Acceleration	Year	Origin
chevrolet chevelle malibu	18	8	307	130	3504	12	1970	USA
ford fiesta	36.1	4	98	66	1800	14.4	1978	USA
bmw 320i	21.5	4	121	110	2600	12.8	1977	Europe

The schema would be something like

[
    {
        "name": "Name",
        "type": "dimension"
    },
    {
        "name": "Maker",
        "type": "dimension"
    },
    {
        "name": "Miles_per_Gallon",
        "type": "measure",
        "defAggFn": DataModel.AggregationFunctions.MAX
    },
    {
        "name": "Displacement",
        "type": "measure",
        "defAggFn": DataModel.AggregationFunctions.MAX
    },
    {
        "name": "Horsepower",
        "type": "measure",
        "defAggFn": DataModel.AggregationFunctions.AVG
    },
    {
        "name": "Weight_in_lbs",
        "type": "measure",
        "defAggFn": DataModel.AggregationFunctions.MIN,
        "format": val => `Total weight in pounds ${val}`
    },
    {
        "name": "Acceleration",
        "type": "measure",
        "defAggFn": DataModel.AggregationFunctions.AVG,
        "displayName": "Acc"
    },
    {
        "name": "Origin",
        "type": "dimension"
    },
    {
        "name": "Cylinders",
        "type": "dimension"
    },
    {
        "name": "Year",
        "type": "dimension",
        "subtype": "temporal",
        "format": "%Y-%m-%d"
    }
]