The Fourier Transform in Simple Terms

The Fourier Transform is a tool that transforms complex stock price movements into simpler, frequency-based components. In a mathematical context, thistransformation is executed through a specified formula that facilitates a detailed analysis of the stock price movements at various frequency levels.

The mathematical foundation of this process lies in the formula F(w) = ∫_(-∞)^(∞) f(x) * e^(-jwx) dx. Here, f(x) represents the time-domain data of astock’s price, and F(w) gives its frequency-domain counterpart.

In the context of a specific stock, f(x) would represent the stock's price movements over a designated period. The Fourier Transform equation helpsdecompose these movements into different frequencies, each associated with a distinct aspect of the stock’s behaviour.

Mathematically, high-frequency components are identified as those where the value of w (angular frequency *) is large. These components capture rapidfluctuations in the stock price, which could be mathematically represented as oscillations occurring over short intervals of the time-domain data, f(x).

Mid-Frequency components are captured when w is at intermediate values. Mathematically, these components identify patterns and cycles that occur atregular, but not rapid, intervals within the time-series data. They signify periodic events or trends impacting the stock’s price.

Low-Frequency components represented mathematically where the value of w is small, these components reflect long-term, slow-changing trends in thestock’s price. They capture the underlying movements in the data f(x) that unfold over extended periods.

When applying the Fourier Transform to the time-series data of Apple Inc.'s stock prices for example, each frequency component reveals specifictrends. 

The high-frequency components might unveil the stock’s sensitivity to daily news or market sentiment, mid-frequency components could reveal pricepatterns associated with recurring events like product launches or quarterly earnings and low-frequency components might highlight long-term trends shaped by macroeconomic factors or the company’soverall growth.

By examining these isolated frequency components mathematically, analysts can quantitatively assess the impact of various influences on the stock'sprice.


(*) Frequency refers to the number of occurrences of a repeating event per unit of time. In thecontext of waveforms and signals, it describes how often a wave’s cycle repeats in a second. The standard unit of frequency is the hertz (Hz), equivalent to one occurrence or cycle persecond.


Angular frequency, often denoted by (omega ), is a measure of how fast something oscillates or cycles in radians per unit of time. It’s related to the frequency of oscillation and is particularly used in the context of waveforms and harmonic oscillations.


The Fourier Transform in layman’s terms…
The Fourier Transform in layman’s terms…

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About the Author

 

 Florian Campuzan is a graduate of Sciences Po Paris (Economic and Financial section) with a degree in Economics (Money and Finance). A CFA charterholder, he began his career in private equity and venture capital as an investment manager at Natixis before transitioning to market finance as a proprietary trader.

 

In the early 2010s, Florian founded Finance Tutoring, a specialized firm offering training and consulting in market and corporate finance. With over 12 years of experience, he has led finance training programs, advised financial institutions and industrial groups on risk management, and prepared candidates for the CFA exams.

 

Passionate about quantitative finance and the application of mathematics, Florian is dedicated to making complex concepts intuitive and accessible. He believes that mastering any topic begins with understanding its core intuition, enabling professionals and students alike to build a strong foundation for success.