1 files changed, 57 insertions, 0 deletions
diff --git a/lib/summation.c b/lib/summation.c
new file mode 100755
index 0000000..6d0020b
--- /dev/null
+++ b/lib/summation.c
@@ -0,0 +1,57 @@
+// Summation
+//
+// summation - sum
+//
+// Calculates the sum of the past k values
+//
+// y_i = sum_{j=i-k+1}^{i}[x_j]
+//
+// Inputs:    1
+// Outputs:   1
+// Constants: 0
+
+
+#include "ts.h"
+
+
+typedef struct {
+    uint_t k;
+} ts_summation_params_t;
+
+ts_parameter_t const ts_summation_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 1, .params_size = sizeof(ts_summation_params_t) };
+
+
+uint_t ts_summation_offset( ts_constant_t const *c )
+{
+	( void )c;
+	return ( c ? ((ts_summation_params_t *)c)->k > 0 ? ((ts_summation_params_t *)c)->k - 1 : 0 : 0 );
+}
+
+int ts_summation(
+	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_summation_p );
+	if ( !c ) return -1;
+	uint_t k = ((ts_summation_params_t *)c)->k;
+	if (k == 0 || n < k) return -1;
+	
+	uint_t xi = 0;
+	uint_t yi = k;
+
+	y[0][k - 1] = 0;
+
+	for( ; xi < k; xi++ )
+	{
+		y[0][k - 1] += x[0][xi];
+	}
+
+	for( ; xi < n; xi++, yi++ )
+	{
+		y[0][yi] = x[0][xi] + y[0][yi - 1] - x[0][xi - k];
+	}
+	return 0;
+}
+