If a positive value is supplied for parameter "pca.pcathresh" (and the PCA model is included in parameter "modelorder" ), then the number of PCA components to remove on each iteration is determined dynamically using a sigma-clipping algorithm, and the number of components removed can change between iterations. A potential problem with this is that the number of components removed may not settle down to a fixed value but may continue to change, thus slowing convergence. To prevent this, a non-zero value may be specified for " pca.pcathresh_freeze" , which prevents any further change to the number of components removed. If the value of pca.pcathresh_freeze is between zero and 1.0, it specifies the normalised mapchange value at which to freeze the number of removed components. If the pca.pcathresh_freeze value is greater than 1 it specifies an integer number of iterations, in addition to the initial AST-skip iterations, after which the number of removed components should be frozen. If pca.pcathresh_freeze is negative, the number of components to remove is frozen as soon as any initial AST-skip iterations have been performed. [0.0]

MAKEMAP, CALCQU