http://rpubs.com/deleeuw/83572. The paper uses monotone B-splines and majorization in an R function that implements nonlinear generalizations of PCA, multiple regression, image analysis, SEM.? And much more. This extends methods in the CRAN package `aspect`. The theory has been around for 30 years but the technical improvements using R, RStudio, knitr are impressive, if I say so myself. The markdown file which contains all R and C code is at http://gifi.stat.ucla.edu/aspect.Rmd ==Jan de Leeuw, Professor Emeritus, UCLA Statistics 8 N Stafford Street, Portland, OR 97217 ? 971-254-9331 email: deleeuw at stat.ucla.edu ? homepage: http://gifi.stat.ucla.edu