- a vector is a list of numbers that represents something. - used to encode data points in machine learning so that algorithms can process more efficiently. - extremely important in [[{3.1} the algorithm is a giant system|recommendation systems]]. - vectors can be used to represent: - **text** → words or documents can be represented as vectors, e.g. where each number represents the importance of a term in a file, or some other semantic meaning. - **images** → components of the vector represent each pixel; a 28x28 grayscale image would have 784 numbers in its vector. - **features** → where each attribute is a component of the vector. for example: | house id | bedrooms | bathrooms | sq ft | vector representation | | -------- | -------- | --------- | ----- | --------------------- | | 001 | 3 | 1 | 1500 | [3, 1, 1500] | | 002 | 2 | 2 | 1500 | [2, 2, 1500] | | 003 | 3 | 2 | 1750 | [3, 2, 1750] |