The 9 Degrees of Freedom-Razor IMU incorporates three sensors, an ITG-3200 (MEMS triple-axis gyro), ADXL345 (triple-axis accelerometer), and HMC5883L (triple-axis magnetometer) - to give you nine degrees of inertial measurement. The outputs of all sensors are processed by an on-board ATmega328 and output over a serial interface. K-means clustering is a type of unsupervised learning, which is used when you have unlabeled data (i.e., data without defined categories or groups). The goal of this algorithm is to find groups in the data, with the number of groups represented by the variable K. The algorithm works iteratively to assign each data point to one of K groups based on the features that are provided. Data points are clustered based on feature similarity.

Papers:

W. Tangwongcharoen, and W. Titiroongruang, "Determining Golf Swing Patterns Using Motion Sensors for Injury Prevention," Proceedings of The International MultiConference of Engineers and Computer Scientists 2017, 15-17 March, 2017, Hong Kong, pp765-769

K. Shirota, K. Watanabe, Y. Kurihara, "Measurement and analysis of golf swing using 3-D acceleration and gyro sensor", SICE Annual Conference Akita University, pp. 356-360, 2012.

Zar, J.H. (1984) Biostatistical Analysis. Prentice-Hall International, New Jersey, pp 43–45.