En las siguientes expresiones, se muestran las cinco entropias wavelets, \(\phi_{i}\) es nivel y \((\phi_{i})_{w_{i}}\) los coeficientes de \(\phi_{i}\) en una base ortonormal.
The (nonnormalized) Shannon entropy:
\(E_{1}(\phi_{i})=-\displaystyle\sum_{i}{\phi_{i}}^{2}*\log(\phi_{i}^{2})\)
Norm entropy with \(1\leq p\):
\(E_{2}(\phi_{i})=\displaystyle\sum_{i}|{\phi_{i}}|^{p}=||{\phi_{i}}||_{p}^{p}\)
The log energy entropy:
\(E_{3}(\phi_{i})=\displaystyle\sum_{i}(\log{\phi_{i}}^{2})\)
The threshold entropy:
\(E_{4}(\phi_{i})=1\) if \(|\phi_{i}|>p\)
The SURE entropy:
\(E_{5}(\phi_{i})=n-|\phi_{i}|\leq p\}+\displaystyle\sum_{i}\min(\phi_{i}^{2},p^{2})\)
Donde P is the threshold.

El algoritmos \ref{alg1} , representa la extraccion del vector formado por \(21\) caracteristicas propuestas para este estudio.