Eigenvalues and eigenvectors for dummies

Eigenvalues and eigenvectors are mathematical concepts often used in linear algebra, with applications in fields such as physics, engineering, computer science, and data analysis.

While these terms might seem intimidating at first, understanding them is not as difficult as it seems. In this article, we will simplify these concepts and explain their importance.

Eigenvalues and Eigenvectors: The Basics

To understand eigenvalues and eigenvectors, we first need to know what a linear transformation is.

A linear transformation is a function that takes a vector (a list of numbers) as input and produces another vector as output while preserving the structure of the input vector.

For example, scaling (resizing) and rotating objects are common linear transformations in computer graphics.

Now, let’s introduce eigenvalues and eigenvectors:

  1. Eigenvector: An eigenvector is a non-zero vector that, when multiplied by a linear transformation, only changes by a scalar factor. In other words, the direction of the eigenvector remains unchanged after the transformation.
  2. Eigenvalue: The eigenvalue is the scalar factor by which an eigenvector is stretched or compressed when multiplied by a linear transformation. It is a measure of how much the eigenvector changes during the transformation.

Why Are Eigenvalues and Eigenvectors Important?

Eigenvalues and eigenvectors are useful for various reasons:

  1. Stability analysis: In fields like engineering and physics, eigenvalues can help determine the stability of a system. For instance, if all eigenvalues have negative real parts, a dynamic system is considered stable.
  2. Data analysis: In statistics and data science, eigenvalues and eigenvectors are used in techniques like Principal Component Analysis (PCA) to reduce the dimensionality of data while preserving its essential structure.
  3. Computer graphics: In computer graphics, eigenvalues and eigenvectors are used to transform, rotate, and scale objects in 3D space.
  4. Quantum mechanics: In quantum mechanics, eigenvectors and eigenvalues are used to describe the state of a system and the possible outcomes of measurements.

A Simple Example

Let’s look at a simple example to better understand eigenvalues and eigenvectors. Consider the following 2×2 matrix representing a linear transformation:

| 2 1 | | 1 2 |

Our goal is to find an eigenvector and its corresponding eigenvalue for this matrix. To do this, we first need to solve the following equation:

(Matrix – (Eigenvalue * Identity Matrix)) * Eigenvector = 0

For our example:

| (2 – λ) 1 | | x | | 0 | | 1 (2 – λ) | | y | = | 0 |

Solving this equation, we find two eigenvalues, λ1 = 1 and λ2 = 3. For each eigenvalue, we can find a corresponding eigenvector:

Eigenvalue λ1 = 1: Eigenvector v1 = | 1 | (or any multiple of this vector) | -1 |

Eigenvalue λ2 = 3: Eigenvector v2 = | 1 | (or any multiple of this vector) | 1 |


Eigenvalues and eigenvectors are fundamental concepts in linear algebra with numerous applications across various fields.

Although they might seem daunting at first, understanding them is achievable with a simplified explanation like the one provided in this article.

Remember that eigenvectors are special vectors that maintain their direction after a linear transformation, while eigenvalues describe how much these vectors are scaled during the process.

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