**2. Pattern recognition**

In analytical chemistry when we have the data set, it is important find similarities and differences between samples based on measurements. For this is necessary to use methods according with information about the samples. And can be: Unsupervised (HCA and PCA) and Supervised methods (KNN)

#### **2.1. Unsupervised methods**

In this group there are two methods: Hierarchical Cluster Analysis (HCA) and Principal Components Analysis (PCA), and the goal is to evaluate if there is any clustering in data set without using the class about samples.
