{
  "schema": "ml-prep/item@1",
  "item": {
    "id": "pml-book1-ex11.4",
    "area": "machine-learning",
    "topic": "optimization",
    "origin": "external",
    "title": "Reducing elastic net to lasso",
    "skills": [
      "objective-functions",
      "regularization"
    ],
    "priority": "supplementary",
    "difficulty": "hard",
    "estimated_minutes": 15,
    "prerequisites": [
      "l1-norm",
      "l2-norm",
      "linear-regression"
    ],
    "source_id": "pml-book1-2022",
    "locator": {
      "document": "PML Book 1 online draft (2025-04-18), Chapter 11 exercises",
      "label": "Exercise 11.4",
      "page_label": "book p. 412 (PDF p. 442)",
      "solution_pages": "26"
    },
    "links": {
      "problem": "https://github.com/probml/pml-book/releases/download/2025-04-18/book1.pdf#page=442",
      "solution": "https://probml.github.io/pml-book/solns-public.pdf#page=26"
    },
    "selection_note": "Transforms a mixed regularization objective into a standard lasso problem on augmented data.",
    "source_caveat": "The public solution manual predates the dated book draft; the exercise title and task align, but notation may differ.",
    "answer_status": "official-solution"
  }
}