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GOCSpline

GOCSpline

Synopsis

                    GOCSpline;
enum                GOCSplineType;
GOCSpline *         go_cspline_init                     (double const *x,
                                                         double const *y,
                                                         int n,
                                                         unsigned  limits,
                                                         double c0,
                                                         double cn);
void                go_cspline_destroy                  (GOCSpline *sp);
double              go_cspline_get_value                (GOCSpline const *sp,
                                                         double x);
double              go_cspline_get_deriv                (GOCSpline const *sp,
                                                         double x);
double *            go_cspline_get_values               (GOCSpline const *sp,
                                                         double const *x,
                                                         int n);
double *            go_cspline_get_derivs               (GOCSpline const *sp,
                                                         double const *x,
                                                         int n);

Description

Details

GOCSpline

typedef struct {
	double const *x, *y;
	double *a, *b, *c;
	int n;
} GOCSpline;


enum GOCSplineType

typedef enum {
	GO_CSPLINE_NATURAL,
	GO_CSPLINE_PARABOLIC,
	GO_CSPLINE_CUBIC,
	GO_CSPLINE_CLAMPED,
	GO_CSPLINE_MAX
} GOCSplineType;


go_cspline_init ()

GOCSpline *         go_cspline_init                     (double const *x,
                                                         double const *y,
                                                         int n,
                                                         unsigned  limits,
                                                         double c0,
                                                         double cn);

Creates a spline structure, and computes the coefficients associated with the polynoms. The ith polynome (between x[i-1] and x[i] is: y(x) = y[i-1] + (c[i-1] + (b[i-1] + a[i] * (x - x[i-1])) * (x - x[i-1])) * (x - x[i-1]) where a[i-1], b[i-1], c[i-1], x[i-1] and y[i-1] are the corresponding members of the new structure.

x :

the x values

y :

the y values

n :

the number of x and y values

limits :

how the limits must be treated, four values are allowed: GO_CSPLINE_NATURAL: first and least second derivatives are 0. GO_CSPLINE_PARABOLIC: the curve will be a parabole arc outside of the limits. GO_CSPLINE_CUBIC: the curve will be cubic outside of the limits. GO_CSPLINE_CLAMPED: the first and last derivatives are imposed.

c0 :

the first derivative when using clamped splines, not used in the other limit types.

cn :

the first derivative when using clamped splines, not used in the other limit types.

Returns :

a newly created GOCSpline instance which should be destroyed by a call to go_bezier_spline_destroy.

go_cspline_destroy ()

void                go_cspline_destroy                  (GOCSpline *sp);

Frees the spline structure when done.

sp :

a spline structure returned by go_cspline_init.

go_cspline_get_value ()

double              go_cspline_get_value                (GOCSpline const *sp,
                                                         double x);

sp must be a valid spline structure as returned by go_cspline_init.

sp :

a spline structure returned by go_cspline_init.

x :

The value

Returns :

the interpolated value for x, or 0 if an error occurred.

go_cspline_get_deriv ()

double              go_cspline_get_deriv                (GOCSpline const *sp,
                                                         double x);

sp must be a valid spline structure as returned by go_cspline_init.

sp :

a spline structure returned by go_cspline_init.

x :

the value

Returns :

the interpolated derivative at x, or 0 if an error occurred.

go_cspline_get_values ()

double *            go_cspline_get_values               (GOCSpline const *sp,
                                                         double const *x,
                                                         int n);

sp must be a valid spline structure as returned by go_cspline_init. The x values must be sorted in increasing order.

sp :

a spline structure returned by go_cspline_init.

x :

a vector a values at which interpolation is requested.

n :

the number of interpolation requested.

Returns :

a newly allocated array of interpolated values which should be destroyed by a call to g_free when not anymore needed, or NULL if an error occurred.

go_cspline_get_derivs ()

double *            go_cspline_get_derivs               (GOCSpline const *sp,
                                                         double const *x,
                                                         int n);

sp must be a valid spline structure as returned by go_cspline_init. The x values must be sorted in increasing order.

sp :

a spline structure returned by go_cspline_init.

x :

a vector a values at which interpolation is requested.

n :

the number of interpolation requested.

Returns :

a newly allocated array of the n interpolated derivatives which should be destroyed by a call to g_free when not anymore needed, or NULL if an error occurred.
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