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// Center of Gravity
//
// center_of_gravity - COG
//
// 1 - 2 * SUM(i*x_i) / ((k+1) * SUM(x_i)), oscillates around 0
//
// Inputs: 1
// Outputs: 1 (COG)
// Constants: 1 (period)
#include "ts.h"
typedef struct {
uint_t k;
} ts_center_of_gravity_params_t;
ts_parameter_t const ts_center_of_gravity_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 1, .params_size = sizeof(ts_center_of_gravity_params_t) };
uint_t ts_center_of_gravity_offset( ts_constant_t const *c )
{
( void )c;
return ( c ? ((ts_center_of_gravity_params_t *)c)->k - 1 : 0 );
}
int ts_center_of_gravity(
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_center_of_gravity_p );
if ( !c ) return -1;
uint_t k = ((ts_center_of_gravity_params_t *)c)->k;
if (k == 0 || n < k) return -1;
for( uint_t i = k - 1; i < n; ++i )
{
fp_t sum_ix = 0;
fp_t sum_x = 0;
for( uint_t j = 0; j < k; ++j )
{
fp_t idx = (fp_t)(j + 1);
fp_t val = x[0][i - k + 1 + j];
sum_ix += idx * val;
sum_x += val;
}
if( sum_x == 0 )
y[0][i] = 0;
else
y[0][i] = 1.0 - 2.0 * sum_ix / ( ( (fp_t)k + 1.0 ) * sum_x );
}
return 0;
}
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