Values for these parameters can be set by using the subroutines NNSETI, NNSETR, NNSETRD, and NNSETC for Fortran programs or the functions c_nnseti, c_nnsetr, c_nnsetrd, and c_nnsetc for C programs.
          |            |                     |               |                 
Parameter | parameter  |                     |               |
  name    |   type     |  description        | legal values  | default value
          |            |                     |               |                 
------------------------------------------------------------------------------
  adf     | int        | flags if the data   | 0 = no        | 0
          |            | file of algorithmic | 1 = yes       |
          |            | info for display is |               |
          |            | produced (see       |               |
          |            | parameter alg).     |               |
------------------------------------------------------------------------------
  alg     | char       | file name for the   | any file name | "nnalg.dat"
          |            | algorithm display   |               |
          |            | tool (see parameter |               |
          |            | adf).               |               |
------------------------------------------------------------------------------
  asc     | int        | flags if automatic  | 0 = no        | 1          
          |            | scaling is allowed  | 1 = yes       |
------------------------------------------------------------------------------
  bI      | float      | tautness factor that| >= 1.         | 1.5
          |            | increases the       |               |
          |            | effect of the       |               |
          |            | gradients as bI     |               |
          |            | increases.          |               |
------------------------------------------------------------------------------
  bJ      | float      | tautness factor that| >= 1.         | 7.0
          |            | decreases the       |               |
          |            | breadth of the      |               |
          |            | region affected by  |               |
          |            | the gradients.      |               |
------------------------------------------------------------------------------
  dup     | int        | controls whether    | 0 = no        | 0
          |            | duplicate input     | 1 = yes       |
          |            | coordinates are     |               |
          |            | allowed.            |               |
------------------------------------------------------------------------------
  ext     | int        | flags whether       | 0 = no        | 1
          |            | extrapolation is    | 1 = yes       |
          |            | allowed outside the |               |
          |            | convex hull.        |               |
------------------------------------------------------------------------------
  hor     | float      | Specifies the       | >= 0.         | 0.1*(extent of
          |            | amount of horizontal|               | X values in
          |            | overlap to be       |               | output grid in
          |            | included outside of |               | the natgrid 
          |            | the current region. |               | invocation)
------------------------------------------------------------------------------
  igr     | int        | flag indicating if  | 0 = no        | 0
          |            | gradients are to be | 1 = yes       |
          |            | computed.           |               |
------------------------------------------------------------------------------
  magx    | float      | scale factor for    | > 0.          | 1.0
          |            | X coordinate values.|               |
------------------------------------------------------------------------------
  magy    | float      | scale factor for    | > 0.          | 1.0
          |            | Y coordinate values.|               |
------------------------------------------------------------------------------
  magz    | float      | scale factor for    | > 0.          | 1.0
          |            | Z coordinate values.|               |
-------------------------------------------------------------------------------
  non     | int        | flags whether in-   | 0 = yes       | 0
          |            | terpolated values   | 1 = no        |
          |            | are allowed to be   |               |
          |            | negative.           |               |
------------------------------------------------------------------------------
  nul     | float      | the value to be used| Any float     | 0.0
          |            | on output for points|               |
          |            | outside of the      |               |
          |            | convex hull when    |               |
          |            | extrapolation is not|               |
          |            | allowed.            |               |
------------------------------------------------------------------------------
  rad     | int        | flags if slopes and | 0 = radians   | 0
          |            | aspects are returned| 1 = degrees   |
          |            | in radians or       |               |
          |            | degrees.            |               |
------------------------------------------------------------------------------
  sdi     | int        | flags if slopes and | 0 = no        | 0
          |            | aspects are computed| 1 = yes       |
------------------------------------------------------------------------------
  upd     | int        | flags if the output | 0 = N to S    | 1
          |            | array goes from     | 1 = S to N    |
          |            | south to north or   |               |
          |            | north to south.     |               |
------------------------------------------------------------------------------
  ver     | float      | Specifies the       | >= 0.         | 0.1*(extent of
          |            | amount of vertical  |               | Y values in the
          |            | overlap to be       |               | output grid in 
          |            | included outside of |               | the natgrid
          |            | the current region. |               | invocation)
------------------------------------------------------------------------------
  xas     | float      | Contains the        | > 0.          | 1.            
          |            | scale value for     |               |
          |            | automatic scaling   |               |
          |            | of X values in the  |               |
          |            | most recent         |               |
          |            | interpolation call. |               |
------------------------------------------------------------------------------
  yas     | float      | Contains the        | > 0.          | 1.            
          |            | scale value for     |               |
          |            | automatic scaling   |               |
          |            | of Y values in the  |               |
          |            | most recent         |               |
          |            | interpolation call. |               |
------------------------------------------------------------------------------
  zas     | float      | Contains the        | > 0.          | 1.            
          |            | scale value for     |               |
          |            | automatic scaling   |               |
          |            | of Z values in the  |               |
          |            | most recent         |               |
          |            | interpolation call. |               |
------------------------------------------------------------------------------