> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fincept.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Linear Regression (OLS, Lasso, ElasticNet)

> Fits linear regression models with optional regularization. Supports OLS for interpretability, Lasso for feature selection, and ElasticNet for balanced regularization. Returns coefficients, R-squared, and optional predictions. [Tier: ENTERPRISE, Credits: 10]



## OpenAPI

````yaml api-specs/ml.json post /quantlib/ml/regression/fit
openapi: 3.1.0
info:
  title: FinceptQuantLib API - ML
  description: >-
    Machine Learning and Credit Risk module endpoints for FinceptQuantLib API.
    Pro Tier access required (5 credits per request). Covers credit scoring,
    model validation, regression models, clustering, anomaly detection, feature
    engineering, and preprocessing.
  version: 3.0.0
  contact:
    name: Fincept API Support
    url: https://fincept.in
servers:
  - url: https://api.fincept.in
    description: Fincept API Production Server
security:
  - APIKeyHeader: []
tags:
  - name: quantlib-ml
    description: Machine Learning and Credit Risk Analytics
    x-displayName: ML
paths:
  /quantlib/ml/regression/fit:
    post:
      tags:
        - quantlib-ml
      summary: Linear Regression (OLS, Lasso, ElasticNet)
      description: >-
        Fits linear regression models with optional regularization. Supports OLS
        for interpretability, Lasso for feature selection, and ElasticNet for
        balanced regularization. Returns coefficients, R-squared, and optional
        predictions. [Tier: ENTERPRISE, Credits: 10]
      operationId: regression_fit
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - X
                - 'y'
              properties:
                X:
                  type: array
                  description: Feature matrix
                  items:
                    type: array
                    items:
                      type: number
                  example:
                    - - 1.2
                      - 0.5
                    - - 2.1
                      - 1.3
                    - - 0.8
                      - 0.9
                'y':
                  type: array
                  description: Continuous target values (e.g., LGD, house prices)
                  items:
                    type: number
                  example:
                    - 150000
                    - 235000
                    - 185000
                method:
                  type: string
                  description: Regression method
                  enum:
                    - ols
                    - lasso
                    - elastic_net
                  default: ols
                  example: lasso
                alpha:
                  type: number
                  description: Regularization strength (for Lasso/ElasticNet)
                  default: 0.01
                  example: 0.1
                l1_ratio:
                  type: number
                  description: L1/L2 mix for ElasticNet (0=Ridge, 1=Lasso)
                  default: 0.5
                  example: 0.5
                predict_X:
                  type: array
                  description: Optional feature matrix for prediction
                  items:
                    type: array
                    items:
                      type: number
                  example:
                    - - 1.5
                      - 0.7
      responses:
        '200':
          description: Regression results
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                    example: true
                  data:
                    type: object
                    properties:
                      coefficients:
                        type: array
                        items:
                          type: number
                        example:
                          - 85000
                          - 120000
                      intercept:
                        type: number
                        example: 50000
                      r_squared:
                        type: number
                        example: 0.847
                      predictions:
                        type: array
                        items:
                          type: number
                        example:
                          - 197500
        '401':
          $ref: '#/components/responses/UnauthorizedError'
        '402':
          $ref: '#/components/responses/InsufficientCreditsError'
        '422':
          $ref: '#/components/responses/ValidationError'
components:
  responses:
    UnauthorizedError:
      description: Authentication information is missing or invalid
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: string
                example: Invalid API key
    InsufficientCreditsError:
      description: Insufficient credits for this operation
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: string
                example: Insufficient credits. This endpoint requires 5 credits.
    ValidationError:
      description: Request validation error
      content:
        application/json:
          schema:
            type: object
            properties:
              detail:
                type: array
                items:
                  type: object
                  properties:
                    loc:
                      type: array
                      items:
                        type: string
                    msg:
                      type: string
                    type:
                      type: string
  securitySchemes:
    APIKeyHeader:
      type: apiKey
      in: header
      name: X-API-Key
      description: >-
        API key for authentication. Get your key at
        https://api.fincept.in/auth/register

````