Day 1 of 5
⏱ ~60 minutes
Linear Algebra for ML in 5 Days — Day 1

Vectors & Geometry

Vector addition, scaling, dot product, cross product, norms, projections

What You'll Cover Today

Day 1 of Linear Algebra for ML in 5 Days lays the foundation. You cannot skip this — every subsequent lesson builds on what you establish today. Work through every example, run the code, and do the exercise before moving on.

ℹ️
Topics today: dot product, norms, projections. Each section has code you can copy and run immediately.

dot product

Understanding dot product is the core goal of Day 1. The concept is straightforward once you see it in practice — most confusion comes from skipping the mental model and jumping straight to implementation. Start with the model, then write the code.

dot product
# dot product — Working Example
# Study this pattern carefully before writing your own version

class dotproductExample:
    """
    Demonstrates core dot product concepts.
    Replace placeholder values with your real implementation.
    """
    
    def __init__(self, config: dict):
        self.config = config
        self._validate()
    
    def _validate(self):
        required = ['name', 'type']
        for field in required:
            if field not in self.config:
                raise ValueError(f"Missing required field: {field}")
    
    def process(self) -> dict:
        # Core logic goes here
        result = {
            'status': 'success',
            'topic': 'dot product',
            'data': self.config
        }
        return result


# Usage
example = dotproductExample({
    'name': 'my-implementation',
    'type': 'dot product'
})
output = example.process()
print(output)
💡
Key insight: When working with dot product, always start with the simplest possible case that works end-to-end. Complexity is easier to add than simplicity is to recover.

norms

norms is the practical application of dot product in real projects. Once you understand the underlying model, norms becomes the natural next step.

💡
Pro tip: When working with norms, always read the official documentation for the exact version you're using. APIs change between major versions and generic tutorials often lag behind.

projections

projections rounds out today's lesson. It connects dot product and norms into a complete picture. You'll use all three concepts together in the exercise below.

Common Mistakes on Day 1

📝 Day 1 Exercise
Vectors & Geometry — Hands-On
  1. Set up your environment for today's topic: install required tools and verify the basics work before writing any logic.
  2. Implement a minimal working version of dot product using the code example in this lesson as your starting point.
  3. Extend your implementation to incorporate norms — this is where the two concepts connect.
  4. Test your implementation with both valid and invalid inputs. What happens at the boundaries?
  5. Review your code: is there anything you'd name differently? Any function doing more than one thing? Refactor one thing.

Day 1 Summary

  • dot product is the foundation of today's lesson — understand it before moving on.
  • norms is how you apply it in real projects.
  • projections ties the day's concepts together into a complete pattern.
  • Error handling and input validation belong in the first version, not as an afterthought.
  • Read error messages carefully — they usually tell you exactly what's wrong.
Challenge

Extend today's exercise by adding one feature that wasn't in the instructions. Document what you built in a comment at the top of the file. This habit of going one step further is what separates engineers who grow fast from those who stay stuck.

Finished this lesson?