Provided by: libncarg-dev_6.6.2.dfsg.1-4_amd64 bug

NAME

       FX - Given the X and Y coordinates of a point in the grid coordinate system, the function
       FX returns the X coordinate of the point in user coordinate space.

       FY - Given the X and Y coordinates of a point in the grid coordinate system, the function
       FY returns the Y coordinate of the point in user coordinate space.

STATUS

       FX and FY are obsolete, and are supported only to provide compatibility with old NCAR
       Graphics codes. These functions are internally callable from four NCAR Graphics utilities
       -- the Conrec and Conran families, and Vectors and Streamlines. Since the Conpack utility
       has replaced Conrec and Conran for the most part, little needs to be said about the use of
       FX and FY in those utilities.

       For Vectors and Streamlines, however, these routines have been required in order to
       perform custom mappings of the data coordinate space until Version 3.2, when new mapping
       routine were developed to deal more robustly with non-linear transformations of vector
       components. In order to ease the transition for users of the old packages who depend on
       existing custom mappings using FX and FX, however, both utilities have implemented a
       number of compatibility levels. By modifying the compatibility mode parameter, CPM, you
       can choose to map coordinates either using the old FX and FY routines, of using the new
       Version 3.2 routines.

       If you need to create new custom coordinate space mappings, you should use the new mapping
       methods and not use FX and FY, since the internal support for mappings based on these
       functions is frozen at the present level. Any improvements in the code will be directed
       towards users of the new mapping routines only.

SYNOPSIS

       USERX = FX (X,Y)
       USERY = FY (X,Y)

DESCRIPTION

       X           (REAL, input): The X coordinate of a vector location in the grid coordinate
                   system.

       Y           (REAL, input) The Y coordinate of a vector location in the grid coordinate
                   system.

USAGE

       The user does not invoke the functions, FX and FY, directly. Instead the functions are
       invoked internally by an NCAR Graphics utility in order to convert a position in the grid
       coordinate system into user coordinates. By default, calls to any of the primary entry
       points for Vectors and Streamlines utilities that predate Version 3.2 (that is, EZVEC,
       VELVEC, VELVCT, EZSTRM or STRMLN) use FX and FY to map from grid to user coordinates.
       However, by appropriately setting the compatibility mode parameter, CPM, the user can
       choose whether the FX and FY functions or the new mapping routines are invoked when using
       any of the primary entry points, current or obsolete, supported by Vectors and
       Streamlines.

       Unlike the Version 3.2 mapping routines, whose input coordinates are in the data
       coordinate system, FX and FY take input in the grid coordinate system. Therefore, any
       required conversions into the data coordinate system must be performed within the function
       prior to the mapping into user coordinates. Vectors and Streamlines both provide common
       blocks (VVMAP and STMAP, respectively) that may be included by the FX and FY functions to
       supply the information necessary to perform the conversion into data coordinate space. No
       pre-defined mappings are supported using FX and FY. The default versions of these
       functions simply perform an identity mapping from grid to user coordinate space.

       When Vectors employs FX and FY, it (alone) also requires the use of two other functions,
       called MXF and MYF. Their usage is described below:

NAME

       MXF - MXF is a user modifiable function that, given one end point of a vector in both grid
       and metacode coordinates, returns the X coordinate of the other end of the vector in
       metacode coordinates.

       MYF - MYF is a user modifiable function that, given one end point of a vector in both grid
       and metcode coordinates, returns the Y coordinate of the other end of the vector in
       metacode coordinates.

STATUS

       Like FX and FY, MXF and MYF are obsolete and should not be employed when creating new
       custom mapping code.

SYNOPSIS

       METAX = MXF (X,Y,U,V,SFX,SFY,MX,MY)
       METAY = MYF (X,Y,U,V,SFX,SFY,MX,MY)

DESCRIPTION

       X           (REAL, input): The X coordinate of a vector location in the grid coordinate
                   system.

       Y           (REAL, input) The Y coordinate of a vector location in the grid coordinate
                   system.

       U           (REAL, input) The U component of the vector at the data point specified by
                   arguments X and Y.

       V           (REAL, input) The V component of the vector at the data point specified by
                   arguments X and Y.

       SFX         (REAL, input) Scale factor used to convert the vector magnitude to a length in
                   metacode coordinates.

       SFY         (REAL, input) Scale factor used to convert the vector magnitude to a length in
                   metacode coordinates. In the current implementation this value is the same as
                   the value of SFX.

       MX          (INTEGER, input) X coordinate of the vector location in metacode coordinates.

       MX          (INTEGER, input) Y coordinate of the vector location in metacode coordinates.

USAGE

       The user does not invoke the functions, MXF and MYF, directly.  However, any time the
       Vectors utility is accessed with the compatibility mode parameter set such that the FX and
       FY routines are used to map the first endpoint of the vector, the functions MXF and MYF
       are used to determine the second endpoint.  First FX and FY are invoked to determine the
       vector location in user coordinates, then this point is converted into metacode
       coordinates; MXF and MYF are passed the coordinates of the point both in grid space and in
       metacode space, along with the vector components and a scale factor used to convert the
       vector magnitude into a length in the metacode coordinate system.

       The default version of MXF simply multiplies the U component of the vector (the component
       parallel to the X grid axis) by the scale factor, SFX, and adds it to the X coordinate of
       the first point in metacode coordinates, MX. MYF uses the same scale factor, SFX, but
       multiplies by the V component and adds to the Y coordinate in metacode coordinates. These
       values are respectively returned as the function value by each routine. Note that if a
       mapping is anywhere non-linear, the vector directional angle may change across the
       transformation, and an iterative differential technique must be employed to map the second
       endpoint of the vector. When creating a new mapping, the user is strongly urged to use the
       user-modifiable routine VVUMXY, rather than attempting to work with MXF and MYF.

ACCESS

       To use FX, FY, MXF, and MYF load the NCAR Graphics libraries ncarg, ncarg_gks, and
       ncarg_c, preferably in that order.

SEE ALSO

       Online: vectors, streamlines, vectors_params, streamlines_params, vvumxy, stuixy, stumta,
       stumxy.

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.