Table 3.

Feature set.

No.#	FEATURE	DEFINITION
1	Mean	$mean(\mathrm{x})=\overline{x}=\frac{1}{N}{\displaystyle {\sum }_{n=1}^{N}x[\mathrm{n}]}$
2	Absolute Mean	$mean(|\mathrm{x}|)=\overline{\left|x\right|}$
3	Variance	$\mathrm{var}(\mathrm{x})={\sigma }_x^2=\overline{{(x-\stackrel{¯¯}{x})}^2}$
4	Standard deviation	$std(\mathrm{x})={\sigma }^x=\sqrt{\mathrm{var}(\mathrm{x})}$
5	Mode	Values that appear most frequently in data set
6	Median	Middle value in a data set
7	Average Absolute Difference	$mean(|{\mathrm{x}}^{-}|)=\overline{|\mathrm{x}-\overline{x}|}$
8	75th Percentile	Value separating 25% higher data from 75% lower data in a data set.
9	Interquartile range	Difference between 75th and 25th percentile
10	Gradient (only for air pressure data)	The coefficient of first-order linear fitting
11	Coefficients of FFT (Fast Fourier Transform)	Energy of each frequency component