Formula

Formula features are used when we need to create features on top of other features of the same entity. It is commonly used to enrich an entity with more complex calculations that require multiple aggregations or calculations to be done first.

Simple formula feature

In this example, we define simple metric features for the entity customer:

# customer.yml
features:
  
- type: formula
  name: is_active_customer
  data_type: boolean
  sql: IFF((last_login_date > date_add('day', -30, current_date())) and total_orders > 100, true, false)
  features: 
  - feature: last_login_date
  - feature: total_orders
  

On this example, we already have two features on the customer level: last_login_date and total_orders. We use these two features to define wbich customers are active customers.

formula is a special type of feature, which is not reliant on related data assets or related entities like other feature types, as it creates features based on features of the same entity.

type

The feature type. In case of formula features, it should be set to formula.

name

Give the feature a name.

data_type [optional]

Specify the feature data type. If no data_type specified, Lynk will assume the data type is string.

The options for data types are:

string

For any type of string data type

number

For any type of number data type. For example: integer, float, decimal etc..

bool

For boolean data type.

datetime

For any type of time-based data type. For example: date, timestamp, datetime etc..

sql

The formula definition.

Any SQL code applies here as long as:

1. It is based on features already defined on the entity

2. it does not have aggregate functions

In case you have an aggregate function in a formula, you probably need to create another metric feature and then create the formula feature on top of it

features

A list of the features that were included in the formula sql definition.

feature

The feature name for each feature that was included in the formula sql definition.