Loss of fat below the skin in the cheeks, temples, chin, nose, and eye area may result in loosening skin, sunken eyes, and a skeletal appearance. Bone loss, mostly around the mouth and chin, may become evident after age 60 and cause puckering of the skin around the mouth.
Logistic regression allows one to predict a discrete outcome, such as group membership, from a set of variables that may be continuous, discrete, dichotomous, or a mix of any of these. Generally, the dependent or response variable is dichotomous, such as presence/absence or success/failure.
Nonlinear regression. In statistics, nonlinear regression is a form of regression analysis in which observational data are modeled by a function which is a nonlinear combination of the model parameters and depends on one or more independent variables. The data are fitted by a method of successive approximations.