ZhiZhi Gewu

Sign in Subscribe

ZhiZhi Gewu

Why Supervised Learning Works?

Why Supervised Learning Works?

In essence, "Low Training Error + Sufficient Data Relative to Model Complexity → Low Test Error". Supervised learning must work on the SAME distribution. Key Concepts * Training Error (\(\text{Train}_S(f)\)): The error of a model \(f\) evaluated on the training dataset \(S\). * Test Error (\(\text{Test}_D(f)

Matrices Explained

Matrices Explained

Linear Transformations and Matrices Linear Transformations A transformation \(T\) is linear if it satisfies the following two properties: 1. Additivity: For all vectors \(x, y\) in the domain of \(T\), we have \(T(x + y) = T(x) + T(y)\). 2. Homogeneity: For all vectors \(x\) in the domain of \(T\

[Study Note] V and Q Function in RF

[Study Note] V and Q Function in RF

UC Berkeley's CS285 course: lecture 4. The goal of reinforcement learning is to find an optimal policy \(\pi^*\) that maximises the cumulative rewards over time. Define the trajectory \(\tau = (s_0,a_0,s_1,a_1,...) \), which is a sequence of states and actions. The probability under

One Month Later: Getting Back on Track with Updates

One Month Later: Getting Back on Track with Updates

Dear readers, It's been nearly a month since my last post, and I wanted to update you on my recent activities. While my day job has kept me quite busy, I've still managed to explore some fascinating topics in my spare time. I'm pleased

My Current View on Practical Asset Allocation

My Current View on Practical Asset Allocation

Recently, I read "A Fundamental Approach to Personal Investment" by David Swensen. Swensen strongly recommends that investors focus on asset allocation, rather than market timing and security selection, to generate returns. He introduces concepts from Modern Portfolio Theory (MPT) to support this approach. Modern Portfolio Theory: A Brief

[Book Summary] Core Asset Classes: A Fundamental Approach to Personal Investment by David Swensen

[Book Summary] Core Asset Classes: A Fundamental Approach to Personal Investment by David Swensen

Core Asset Classes Defining asset classes combines art and science in an attempt to group like with like, seeking as an end result a relatively homogeneous collection of investment opportunities. The author discusses the characteristics of core asset classes: * Contribute basic, valuable, and differentiable characteristics to a portfolio * Rely on

[Book Summary] A Fundamental Approach to Personal Investment by David Swensen

[Book Summary] A Fundamental Approach to Personal Investment by David Swensen

Overview: Sources of Return * Capital markets provide three tools for investors to generate returns: asset allocation, market timing, and security selection. * Asset Allocation: long-term decision regarding the proportion of assets that an investor chooses to place in particular asset classes. * Market Timing: deviations from the long-term asset-allocation targets. It represents