initial commit: ts time series analysis library v0.1.0

- 354 financial and mathematical time-series indicators
- Uniform C11 API with consistent function signatures
- 349 passing tests with -Werror
- Static and shared library builds
- pkg-config integration
- Python bindings
- Fuzzing and sanitizer support
- Security hardening flags

1 files changed, 60 insertions, 0 deletions

diff --git a/lib/bollinger_lower.c b/lib/bollinger_lower.c
new file mode 100644
index 0000000..05a0883
--- /dev/null
+++ b/lib/bollinger_lower.c
@@ -0,0 +1,60 @@
+// Bollinger Lower Band
+//
+// bollinger_lower - BB lower
+//
+// Lower band: SMA - mult * stddev
+//
+// Inputs:    1
+// Outputs:   1 (Lower Band)
+// Constants: 2 (period, std multiplier)
+
+#include <math.h>
+#include "ts.h"
+
+
+typedef struct {
+    uint_t k;
+    fp_t std_mult;
+} ts_bollinger_lower_params_t;
+
+ts_parameter_t const ts_bollinger_lower_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 2, .params_size = sizeof(ts_bollinger_lower_params_t) };
+
+
+uint_t ts_bollinger_lower_offset( ts_constant_t const *c )
+{
+	( void )c;
+	return ( c ? ((ts_bollinger_lower_params_t *)c)->k - 1 : 0 );
+}
+
+int ts_bollinger_lower(
+	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_bollinger_lower_p );
+	if ( !c ) return -1;
+	uint_t k = ((ts_bollinger_lower_params_t *)c)->k;
+	if (k == 0 || n < k) return -1;
+	fp_t std_mult = ((ts_bollinger_lower_params_t *)c)->std_mult;
+	if (isnan(std_mult) || isinf(std_mult)) return -1;
+
+	for( uint_t i = k - 1; i < n; ++i )
+	{
+		fp_t sum = 0, sum2 = 0;
+		for( uint_t j = 0; j < k; ++j )
+		{
+			fp_t v = x[0][i - k + 1 + j];
+			sum += v;
+			sum2 += v * v;
+		}
+		fp_t mean = sum / k;
+		fp_t variance = sum2 / k - mean * mean;
+		fp_t stddev = variance >= 0 ? sqrt( variance ) : 0;
+		y[0][i] = mean - std_mult * stddev;
+	}
+	return 0;
+}
+
+
+