The integral term of the information entropy unadapted for being a measuring index / 中国医学物理学杂志

ABSTRACT

The information entropy, H = - Pk log Pk, has been proved in this paper to be always positive and invariant for a linear coordinate transformation, so that it can be used as a measuring index. On the contrary, the integral term of the information entropy, H(x) = -f(x) log f(x) dx, is not always positive and invariant for a linear coordinate transformation. Therefore, H(x) can not be used as a measuring index. An example of a probability density function for response of nerve to electric current with different intensities is given to confirm above conclusions.