Time-Series Analysis
The statistics of data ordered in time, covering autocorrelation, stationarity and volatility clustering. Price series are non-stationary, which is why models are usually built on returns rather than prices, and why volatility models such as GARCH exist to capture the tendency of turbulent periods to cluster together.
Feature Engineering
Turning raw market data into inputs a model can use: returns over various horizons, volatility measures, volume ratios, order book imbalance. In practice this determines model quality far more than the choice of algorithm, and it is also where look-ahead bias most often creeps in.
Market Regime Detection
Classifying the market into states such as trending, ranging or high-volatility, often using clustering or hidden Markov models. The value is in switching strategies rather than predicting price: knowing which environment you are in is more reliable than knowing where price goes next.
Reinforcement Learning
Training an agent to learn a trading policy by rewarding outcomes. It is appealing because it optimises the actual objective rather than a proxy, and it is difficult in practice because financial data is limited, non-stationary and noisy, so agents frequently learn the history rather than a general policy.
Alternative Market Data
Inputs beyond price and volume: on-chain activity, social data, funding, positioning. The attraction is that fewer people use it. The reality is that it is often shorter in history, less clean, and harder to validate, so its edge has to be weighed against the difficulty of testing it honestly.