Johnson Curve

Johnson Curve Toolbox for Matlab: analysis of non-normal data using the Johnson family of distributions. The Johnson Curve Toolbox for Matlab is a set of Matlab functions for working with the Johnson family of distributions to analyze non-normal, univariate data sets. Portions of it are based on my port of the AS 99 (Hill et al., 1976) and AS 100 (Hill, 1976) FORTRAN-66 code. The Toolbox provides support for fitting Johnson curves to data based on moments or quantiles; using Johnson transformations to convert Johnson variates to normal variates (and vice versa); generating random numbers from Johnson distributions; calculating probability densities (PDF), cumulative probability densities (CDF), and inverse CDF’s; and calculating likelihoods and goodness-of-fit measures. Examples of fitting Johnson curves to biological, environmental, demographic, and financial data are also provided.