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ft_open, ft_spline, ft_close - function table processing routines


#include <funtab.h>
FunctionTable *ft_open(string fname, int mode, int xcol, int ycol);
real ft_spline(FunctionTable *ft, real x);
int ft_close(FunctionTable *ft);


A FunctionTable is a data structure, defined in <funtab.h>, with which ASCII tables can be used to interpolate values from. The FunctionTable can be considered an opaque pointer: it should be of no concern to the applications programmer what’s inside.

ft_open is used to initialize an interpolation table. Inputs are the filename fname, a mode of interpolation (currently FUNTAB_LINEAR, and FUNTAB_SPLINE have been implemented), and the two columns from the table (1 being the first column) that are used for X and Y.

ft_spline returns a spline interpolated value for a given input value x.

ft_close must be called if you want to free up memory used by these routines.

Function-table Structure

typedef struct FunctionTable {
    string name;        /* ID or filename */
    int mode;           /* lookup mode (one of the FUNTAB_xxx modes) */
    int n;              /* Number of points in table */
    real *x;            /* pointer to array of X values */
    real *y;            /* pointer to array of Y values */
    real *coeff;        /* (spline) coefficients, if used */
    int errors;         /* cumulative errors in interpolation */
} FunctionTable;
from the standard include file funtab.h.


Files larger than MAXLINES (see table(3NEMO) and stdinc.h) may have problems being fully processed.

Linear interpolation isn’t even working.

See Also



Peter Teuben


~/src/kernel/tab    funtab.c

Update History

4-oct-93    Created       PJT
5-mar-94    Documented    PJT

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