Table 2 Calculations of time domain and frequency domain features.
Time domain features | Frequency domain features |
|---|---|
\(TF_{1} = \frac{1}{L}\sum _{i=1}^{L}|x_{i}|\) | \(FF_{1} = \frac{\sum _{j=1}^{n}s_{j}}{K}\) |
\(TF_2 = \sqrt{\frac{1}{L}\sum _{i=1}^{L}\left( x_{i}-\bar{x}\right) ^{2}}\) | \(FF_2 = \frac{\sum _{j=1}^{K}\left( s_{j}-FF_{1}\right) ^{2}}{K}\) |
\(TF_3 = \sqrt{\frac{1}{L}\sum _{i=1}^{L}\left( x_{i}\right) ^{2}}\) | \(FF_3 = \frac{\sum _{j=1}^{K} f_{j} \cdot s_{j}}{\sum _{j=1}^{K} s_{j}}\) |
\(TF_4 = \frac{TF_{3}}{TF_{1}}\) | \(FF_4 = \sqrt{\frac{\sum _{j=1}^{K}\left( f_{j}-FF_{3}\right) ^{2} \cdot s_{j}}{K}}\) |
\(TF_5 = |\operatorname {min}\left\{ x_{i} \mid i=1,2,...,L\right\} |\) | \(FF_5 = \frac{FF_{4}}{FF_{3}}\) |
\(TF_6 = |\operatorname {max}\left\{ x_{i} \mid i=1,2,...,L\right\} |\) | \(FF_6 = \sqrt{\frac{\sum _{j=1}^{K}s_{j}^{2}}{K}}\) |
\(TF_7 = TF_6 - TF_5\) | \(FF_7 = \frac{\frac{1}{K}\sum _{j=1}^{K}\left( s_{j}-FF_{1}\right) ^{4}}{\left[ \frac{1}{K}\sum _{j=1}^{K}\left( s_{j}-FF_{1}\right) ^{2}\right] ^{2}}\) |
