lib/slope.c


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// Slope
//
// slope - slope
//
// Calculates the slope between the current value and the value k samples ago
//
// y_i = ( x_i - x_i-k ) / k
//
// Inputs:    1
// Outputs:   1
// Constants: 0


#include "ts.h"


typedef struct {
    uint_t k;
} ts_slope_params_t;

ts_parameter_t const ts_slope_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 1, .params_size = sizeof(ts_slope_params_t) };


uint_t ts_slope_offset( ts_constant_t const *c )
{
	( void )c;
	return ( c ? ((ts_slope_params_t const *)c)->k : 0 );
}

int ts_slope(
	fp_t * const *y, uint_t y_n,
	fp_t const * const *x, uint_t x_n,
	uint_t n, ts_constant_t const *c
)
{
	TS_PROLOGUE( ts_slope_p );
	if ( !c ) return -1;
	uint_t k = ((ts_slope_params_t const *)c)->k;
	if (k == 0 || n < k) return -1;

	uint_t xi = k;

    fp_t rk = _ts_reciprocal( k );

	for( ; xi < n; xi++ )
	{
		y[0][xi] = ( x[0][xi] - x[0][xi - k] ) * rk;
	}
	return 0;
}