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Lära Neural Networks as Compositions of Functions | Neural Networks as Linear-Algebraic Objects
Mathematical Foundations of Neural Networks

bookNeural Networks as Compositions of Functions

When you think of a neural network, imagine a machine that transforms data step by step, using a precise mathematical structure. At its core, a neural network is not just a collection of numbers or weights; it is a composition of functions. This means the network takes an input, applies a series of operations — each one transforming the data further — and produces an output. Each operation in this sequence is itself a function, and the overall effect is achieved by chaining these functions together.

Note
Definition

Function composition is the process of applying one function to the result of another, written as (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x)). In neural networks, this concept is fundamental: each layer’s output becomes the input for the next, forming a chain of transformations.

This mathematical structure is what gives neural networks their power and flexibility. Each layer in a neural network performs two main actions. First, it applies a linear transformation to its input — this is typically a matrix multiplication with the layer’s weights, plus a bias. Immediately after, it applies a nonlinear activation function such as ReLU or sigmoid. This two-step process — linear map followed by nonlinearity — is repeated for every layer, making the network a deep composition of these alternating operations. The output of one layer becomes the input to the next, and the entire network can be viewed as a single function built by composing all these smaller functions in sequence.

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bookNeural Networks as Compositions of Functions

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When you think of a neural network, imagine a machine that transforms data step by step, using a precise mathematical structure. At its core, a neural network is not just a collection of numbers or weights; it is a composition of functions. This means the network takes an input, applies a series of operations — each one transforming the data further — and produces an output. Each operation in this sequence is itself a function, and the overall effect is achieved by chaining these functions together.

Note
Definition

Function composition is the process of applying one function to the result of another, written as (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x)). In neural networks, this concept is fundamental: each layer’s output becomes the input for the next, forming a chain of transformations.

This mathematical structure is what gives neural networks their power and flexibility. Each layer in a neural network performs two main actions. First, it applies a linear transformation to its input — this is typically a matrix multiplication with the layer’s weights, plus a bias. Immediately after, it applies a nonlinear activation function such as ReLU or sigmoid. This two-step process — linear map followed by nonlinearity — is repeated for every layer, making the network a deep composition of these alternating operations. The output of one layer becomes the input to the next, and the entire network can be viewed as a single function built by composing all these smaller functions in sequence.

question mark

Which statement best describes the role of function composition in neural networks?

Select the correct answer

Var allt tydligt?

Hur kan vi förbättra det?

Tack för dina kommentarer!

Avsnitt 1. Kapitel 1
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