I found the term of "degree of variability" from a academic paper. It seems to be used to determine the cutoff of a continuous variable. The most drastic change point was used as the cutoff. In the picture below, the red line was the so-called degree of variability. I dont know what does it mean and why the inflection point can be used as the cutoff. How to calculate it, any code if possible?
**Reference: Hiromi Nakamura, et al. Genomic spectra of biliary tract cancer. Nature Genetics 2015.**https://www.nature.com/articles/ng.3375#MOESM54
In the legend of the Supplementary Figure S1, it said that "... The most drastic change point in the mutation rate was chosen for the cutoff to discriminate hypermutated cases from non-hypermutated ones."