## Mathematical notation for the curious

Each chapter contains a small section dedicated to the formulation of the algorithms for those interested in the mathematical concepts behind the science and art of machine learning. These sections are optional and defined within a tip box. For example, the mathematical expression of the mean and the variance of a variable *X* mentioned in a tip box will be as follows:

### Tip

**Convention and notation**

This book uses zero-based indexing of datasets in the mathematical formulas.

M1: A set of *N* observations is denoted as *{xi} = x _{0}, x_{1}, … , x_{N-1}*, and the arithmetic mean value for the random value with

*xi*as values is defined as: