*4.3. Feature Extraction*

Feature extraction is a crucial part of machine learning and has a great influence on the classification performance. Instead of achieving a high accuracy by some complex features in Section 3.1, we aim to evaluate the context impacts and use some popular features in our research. Mean, variation, min, max, energy, skewness, kurtosis, FFT amplitudes, mean-crossing rates and RMS were extracted from the sensor data as features.
