Building Cool Stuff with AI

Data Scientist, ML Engineer, Independent AI Researcher

I’m Fabian Landeros. This is where I write about experiments, research notes, and small ideas I want to understand better.

  • Data scientist and AI engineer at tech startups from 2020 to 2026.
  • M.S. in AI and machine learning from Colorado State University, 2023.
  • B.A. in Economics from Harvard University, 2018.
  • Currently considering a pivot toward a PhD and AI safety research.

Fabian Landeros

Recent Writing

A Neural Network from Scratch, With Every Matrix Explained

Machine Learning
In this notebook we will build a small neural network in pure NumPy and explain every major tensor along the way.
Apr 1, 2026
Fabian

Building Logistic Regression from Scratch

Machine Learning
If you want to truly understand deep learning, you have to look under the hood. While libraries like TensorFlow and PyTorch make it incredibly easy to build models with a…
Mar 20, 2026
Fabian

Learning URDF and Robot Anatomy

Robotics
Hey everyone! I’m currently diving headfirst into the world of robotics. If you’ve ever wanted to simulate a robot, you quickly realize that before you can make it move, you…
Mar 5, 2026
Fabian

Summary of Chapter 4: Dynamic Programming

Reinforcement Learning
If you are reading Richard Sutton and Andrew Barto’s classic book, Reinforcement Learning: An Introduction, Chapter 4 introduces a concept that sits at the very foundation…
Feb 20, 2026
Fabian

Automating B2B Lead Generation with AI and Intelligent Regex

AI Agents
A technical deep dive into building LNKD-AI, a browser-based automation tool for high-precision data enrichment.
Jan 21, 2026
Fabian

Summary of Chapter 3: Finite MDP

Reinforcement Learning
This chapter formalizes the reinforcement learning problem using the framework of Markov Decision Processes (MDPs).
Jan 10, 2026
Fabian

Summary of Chapter 2: 10 arm testbed

Reinforcement Learning
Notes based on the book Sutton, R. S., & Barto, A. G. (2018). Reinforcement learning: An introduction. MIT press.
Jan 10, 2026
Fabian

Summary of Chapter 1: The Reinforcement Learning Problem

Reinforcement Learning
Notes based on the book Sutton, R. S., & Barto, A. G. (2018). Reinforcement learning: An introduction. MIT press.
Jan 10, 2026
Fabian

LinUCB for ad selection

Reinforcement Learning
This guide details the Contextual Upper Confidence Bound (LinUCB) algorithm.
Jan 10, 2026
Fabian

Building collaborative and content based reccomendation systems

Machine Learning
Imagine you’re scrolling through Netflix, trying to decide what to watch. Netflix shows you personalized recommendations - movies and shows it thinks you’ll love. How does…
Nov 23, 2025
Fabian

Building a Dual-Pipeline Name Anomaly Detection System with FAISS and Embeddings

Machine Learning
Detecting synthetic identities at scale using semantic embeddings and character-level features
Nov 1, 2025
Fabian

Tesseract vs. EasyOCR — From Quick Wins to Robust Pipelines

Machine Learning
I wrote this post because I had to re-learn OCR recently. I kept forgetting the details, configs, and gotchas — so this is my reference to stay sharp. If you’re in the same…
Aug 21, 2025
Fabian

Building Real-World AI Systems with PydanticAI: Lessons from Anthropic’s Agent Design Patterns

AI Agents
As AI continues to reshape industries—from legal and healthcare to marketing and customer service—developers face a growing need to build robust, modular, and intelligent…
May 21, 2025
Fabian

Level Up Your SmolAgents: Practical Patterns for Building Effective Agents

AI Agents
The world of AI is buzzing with excitement about agents, and rightfully so. However, amidst the hype surrounding complex frameworks and specialized libraries, a crucial…
Feb 21, 2025
Fabian

Building Intelligent Customer Service Agents with Pydantic-AI and LLMs

AI Agents
Man I was blown away by how simple and effective building agents in pydantic has been for me this weekend.
Jan 19, 2025
Fabian

Marketing Mix Model Comparison

Marketing Analytics
Imagine trying to bake a cake without knowing how much flour, sugar, or eggs to use. You might end up with a disaster! Similarly, in marketing, blindly allocating budgets…
Oct 26, 2024
Fabian

Identifying Fraud with Isolation Forest

Machine Learning
Fraud detection is a critical task across various industries, from finance to e-commerce. Traditional rule-based systems often struggle to keep up with the evolving tactics…
Oct 17, 2024
Fabian

Email Campaign Effectiveness Predictor

Marketing Analytics
In this blog post, we’ll develop a model that predicts the likely open rates, click-through rates, and conversion rates for email campaigns based on historical data and…
Oct 13, 2024
Fabian

Markov decision process intuition - marketing example

Reinforcement Learning
Markov Decision Processes (MDPs) might sound like a complex mathematical concept, but they’re incredibly useful for making decisions in uncertain environments. In this post…
Oct 6, 2024
Fabian

ad-optimization-with-multi-armed-bandits

Marketing Analytics
Imagine you’re running a website with multiple ad variants. Which ad should you show to maximize clicks? This is a perfect application for the multi-armed bandit (MAB)…
Oct 2, 2024
Fabian

Building and Optimizing a Customer Segmentation Model

Marketing Analytics
In today’s data-driven marketing landscape, understanding your customers is crucial for tailoring effective marketing strategies. One powerful technique for gaining these…
Aug 13, 2024
Fabian

Understanding Multi-Armed Bandits: A Gateway to Reinforcement Learning

Reinforcement Learning
Multi-armed bandits (MAB) represent one of the simplest yet most profound examples of the exploration-exploitation dilemma in reinforcement learning. In this blog post…
Aug 1, 2024
Fabian

Understanding Markov Decision Processes in Deep Reinforcement Learning

Reinforcement Learning
Markov Decision Processes (MDPs) form the theoretical backbone of modern reinforcement learning, including deep reinforcement learning. In this post, we’ll explore how MDPs…
Jul 21, 2024
Fabian

The Bellman Equation: The Foundation of Deep Reinforcement Learning

Reinforcement Learning
The Bellman equation, named after Richard Bellman, is one of the most fundamental concepts in reinforcement learning. It provides a recursive relationship between the value…
Jul 11, 2024
Fabian

Reinforcement Learning: A Comprehensive Overview

Reinforcement Learning
These equations form the foundation for many RL algorithms, which aim to find or approximate the optimal value functions and, consequently, the optimal policy.
May 11, 2024
Fabian

Marketing Mix Modeling

Marketing Analytics
Marketing Mix Modeling (MMM) is a powerful technique used to measure the effectiveness of various marketing activities and understand how they contribute to sales or other…
May 6, 2024
Fabian

Quant Trading: Asset Class Selection

Quant Finance
As a seasoned quantitative trader who relies on statistical analysis to thrive in the dynamic world of trading, one of the fundamental questions that drives my strategy is…
Apr 12, 2024
Fabian

Scraping home prices in Ensenada Mexico

Data Science
Nestled in the heart of Ensenada, Baja Califronia, Mexico is an amazing port city that has always been a part of my life,(since Covid) I’ve built a home that is not just a…
Apr 1, 2024
Fabian

Learning Statistics and Probability with SciPy and Python

Data Science
This Jupyter Notebook provides a comprehensive guide to the fundamentals of statistics and probability, using SciPy and Python for practical implementation and visualization.
Mar 21, 2024
Fabian

Gradient Descent Explained: The Engine Behind Machine Learning

Machine Learning
Gradient Descent is an optimization algorithm used to find the minimum of a function.
Feb 12, 2024
Fabian

Navigating the LLM Landscape: A Guide to Key Papers

AI Research
I am keeping a list of the papers which i think are the most important. why i dotn really know. just to make it easier fro me.
Nov 22, 2023
Fabian

Data Discretization: A winning strategy

Data Science
Data discretization is a powerful technique that can significantly improve your machine learning models’ performance. In this tutorial, we’ll explore practical…
Nov 12, 2023
Fabian

The Common Mistakes You’re Making With A/B Testing And How To Avoid Them

Marketing Analytics
A/B testing is one of the most powerful tools in a marketer’s toolkit. By showing different variants of a page to different segments of users, you can directly measure the…
Nov 1, 2023
Fabian

A/B Testing Demystified

Marketing Analytics
A/B testing, also known as split testing, is a powerful technique employed by data engineers and marketers to evaluate the performance of two or more variants of a webpage…
Jan 18, 2023
Fabian
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