The mutative factor function (<b>Eq.7</b>) used in conservation-mutation correlation analysis (CMCA).

<p>The curves are computed according to Eq.7. The horizontal coordinates are the integer position frequencies <i>f_k,l</i> of amino acids in protein database, and the vertical coordinates are the mutative factors. The <i>n_l</i> is the amino acid types at position <i>l</i>. In calculations the protein sample number N is 100. When the frequency of amino acid <i>k</i> takes the average value <i>f_k,l</i> = N/<i>n_l</i>, all curves have the maximum values, and when the amino acid types at position <i>l</i> has the largest value (<i>n_l</i> = 20), the mutative factor gets the largest value 19.