Derived variable

A wide range of mathematical transforms can be applied using this option. The selected operation is applied to all elements of the data set. The data set may be observations, interpolated surface, cross-validation errors, or a previously transformed variable.

Linear transform
Change the units or rescale the data by specifying a constant and slope.

Nonlinear transforms
Used mainly to reduce variance in the data. The inverse transform is applied automatically following interpolation, if desired. Such an option appears when the Begin Interpolation is selected. The available nonlinear transforms are:

Log [ln(x)]
Exponential [exp(x)]
Power [x^p]
Box-Cox [(x^p)/p]
Logistic [ln[x/(1-x)]]
Angular [arcsin(sqrt(x))]
Trigonometric [sin(x) or cos(x)]

Average
Use this option to take the average of several data files. Each file must have the same dimension. This option can be used to create a monthly or annual average of a quantity prior to (or subsequent to) interpolation.

Formula
Using an equation editor, a user can create new variables and perform the interpolation directly on these new variables. If desired, the operations creating the variable are automatically inverted following interpolation, to restore physical meaning to the interpolation variable.

Variograms

Using this option, a variogram is fitted to the data set.

Constrain Lat/Lon

The domain of a dataset can be limited to a rectangle in the latitude-longitude plane. To use this option, the user enters a bounding pair of latitudes and longitudes.

Constrain Values

The values in a dataset can be constrained to lie within specified minimum and maximum values.