The Modern Mathematics of Deep Learningexplained for non-mathematicians

Finite measure and L2

Penguin learning project

The project uses 342 complete Palmer penguin records: 240 training-pool and 102 held-out rows. The selected training rows determine feature scaling and model parameters. Source CSV

This project trains weights with softmax, unlike the homepage lab, which uses nearest species averages. Same penguin measurements; different classification methods. Predictions can differ.

Probability and expectation · Describe random variables and their averages under a law.

Project vectors have two features; the training matrix has n rows and two columns. Mathematical tools may operate on these values when their assumptions apply.

Consider this concept alongside the project; its source assumptions may differ. These observations do not prove a theorem.

Input: 12 × 2; Held-out evaluation: 102 · #58 · 40.6 mm, 193 mm. Known answer: Adélie; Prediction: Adélie · [≈0.7383, ≈0.2444, ≈0.01737].

Used in these source sections: 1.2 Learning from examples

A measure μ assigns sizes to measurable sets. The L²(μ) norm squares function values, integrates with respect to μ, and takes the square root.

The measure determines how values contribute to the norm.

Source formula example

σ\sigma

illustration · A finite measure is σ-finite; general measures can require integration over infinitely many values.

Symbols

μμ
A σ-finite reference measure in the density example.
σ−finiteσ-finite
The domain is a countable union of finite-measure sets.
L2(μ)L²(μ)
Square-integrable functions under μ.

Source formula example

This source example uses its own inputs and assumptions. Editing it does not change the project.

Edit a value or the code, then run the example. This is a finite demonstration, not a proof of the paper’s theorem.

This example’s data flow

Initial values in code

  • values = [1, 3]
  • weights = [0.5, 0.5]

Calculated here

Result expression: { values, weights, norm: Math.sqrt(values.reduce((s, v, i) => s + weights[i] * v * v, 0)), }

Returns

Example result
values
array (2 items): [1, 3]
weights
array (2 items): [0.5, 0.5]
norm
≈2.236

Read numbers from input and return the result. JavaScript basics.

Result

Enable JavaScript to run this example.

Technical statement

The numerical values are invented. A finite measure is σ-finite; general measures can require integration over infinitely many values.

Source: Inline notation