transformation: transformation function. Defaults to no transformation
centering: string, giving the value used to center the covariate; can be "mean" or "median", in which case this value will be computed from the data, 'none' or 0 for no centering, or a value given by the user. Defaults to the median value over the dataset.
verbose: a boolean, prints messages during the execution of the function if TRUE. Defaults to FALSE.