Table of Cssgrid control parameters

The following table summarizes all of the parameters used for controlling the behavior of Cssgrid.

Values for these parameters can be set by using the subroutines CSSETI, CSSETR, CSSETD for Fortran programs or the functions c_csseti, c_cssetr, and c_cssetd for C programs. or cssetp for NCL.

More in-depth understanding of the parameter settings can be obtained from reading Dr. Renka's articles in the ACM Transactions on Mathematical Software, Vol. 23, No 3, September 1997.

Parameter name Parameter type Description Legal values Default value
sig float value of the tension factor for the splines any non-negative value (0. yields cubic splines; large values yield linear interpolation) 1.
tol float Tolerance to use in calculating gradient differences to terminate the iteration sequence when computing global gradients any positive value. 0.01
ttf float Tolerance to use in determining how accurately each tension factor should be calculated to approximate its optimum value any positive value. 0.01
nls int Number of nodes to use in the least squares fit. greater than or equal to 4 10
nsg int Maximum number of iterations to use in the algorithm for computing automatic tension factors greater than or equal to 2 10
isg int Flag to revert to calculating automatic tension factors rather than use a constant tension. Using a constant tension is effected by setting a value for the control parameter sig. If isg is 0, then a tension array is used, otherwise a constant tension is used. Any integer 0
igr int Flags whether global or local gradients are used (1 implies global, anything else implies local). Any integer 1
mvl float Fill value to use in returns for NCL functions. Used only if mvl has been changed from its default. Any float -8.

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