ARTS built-in documentation server
Workspace Method jacobianSetFuncTransformation
Sets the functional transformation of the last element of
See below for a general description of how retrieval transformations
are defined. Transformations are not applied by methods such asyCalc.
Instead, the method jacobianAdjustAndTransform must be called to
activate the transformations.
The following transformations can be selected (by *transformation_func*):
log : The natural logarithm
log10 : The base-10 logarithm
atanh : Area hyperbolic tangent
none : No transformation at all
This method needs only to be called if a functional transformation
is wanted. Default is to make no such tranformation at all (i.e.
the option "none" exists only for reasons of flexibility).
The log-options are applied as log(z-z_min) and log10(z-z_min).
The default for *z_min* is zero, but by changing it the lower limit
for z can be changed. Note that *z_min* becomes the lower limit for
allowed values of z. The GIN *z_max* is here ignored.
For the atanh-option, also *z_max* is considered. This transformation
is applied as atanh((2(z-z_min)/(z_max-z_min))-1). As above,*z_min*
is lower limit for allowed values of z. On the other hand, *z_max*
eines the upper limit for z.
The GIN *transformation_func* is so far only used for atanh. The parameter
specifies the maximum allowed value allowed for u. That is, the valid
range for u becomes ]0,tfunc_parameter[. Note that log and log10
demands/ensures that u > 0, but implies no upper limit.
General handling of retrieval units and transformations:
Default is that quantities are retrieved as defined in ARTS, but
both some unit conversion and transformations are provided. These
operations are applied as:
x = A * ( f(u(z)) - b )
z is the quantity as defined ARTS
u represents the change of unit
f is the transformation function
A and b define together an affine transformation
x is the retrieved quantity
For example, this systen allows to retrive a principal component
representation (A and b) of the log (f) of relative humidity (u).
Change of unit is selected by the quantity specific jacobian-add
methods (so far only at hand for gas species).
Activating a transformation function is done by this method. Note
that the functions are defined as the transformation from z to x.
For more details on affine transformations, see
Authors: Patrick Eriksson, Simon Pfreundschuh