feat: initial release

Assisted-by: GLM 5.3 Flash

stats/quantile_test.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package stats
+
+import (
+	"math"
+	"strings"
+	"testing"
+)
+
+// TestQuantile pins linear interpolation between order statistics.
+func TestQuantile(t *testing.T) {
+	a := mustFloats(t, []float64{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, 10)
+	q, err := Quantile(a, []float64{0.25})
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Linear interpolation: position 0.25*(9)=2.25 lands between 3 and 4.
+	if v := q.FloatAt(0); math.Abs(v-3.25) > 1e-9 {
+		t.Errorf("q25: %v, want 3.25", v)
+	}
+	med, _ := Quantile(a, []float64{0.5})
+	if v := med.FloatAt(0); math.Abs(v-5.5) > 1e-9 {
+		t.Errorf("median quantile: %v", v)
+	}
+}
+
+// TestQuantileDegenerateInputs pins the guard that used to panic:
+// Quantile on an empty sample.
+func TestQuantileDegenerateInputs(t *testing.T) {
+	empty := mustFloats(t, []float64{}, 0)
+	if _, err := Quantile(empty, []float64{0.5}); err == nil {
+		t.Error("Quantile empty: expected error")
+	}
+}
+
+// TestBinCounts counts values in equally wide bins.
+func TestBinCounts(t *testing.T) {
+	vals := mustFloats(t, []float64{-3, 5, 12, 25}, 4)
+	counts, err := BinCounts(vals, 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if counts.Len() != 2 {
+		t.Fatalf("counts len: %d", counts.Len())
+	}
+	if c1 := counts.FloatAt(0); c1 < 1 {
+		t.Errorf("first bin empty: %v", counts.RawFloats())
+	}
+}
+
+// TestComplexStatsErrors pins the refusals for complex input: no
+// ordering, so no median, standard deviation or histogram.
+func TestComplexStatsErrors(t *testing.T) {
+	c := mustComplexes(t, []complex128{complex(1, 1)}, 1)
+
+	if _, err := Median(c); err == nil || !strings.Contains(err.Error(), "no median") {
+		t.Fatalf("Median complex: %v", err)
+	}
+	if _, err := Std(c); err == nil || !strings.Contains(err.Error(), "no float standard deviation") {
+		t.Fatalf("Std complex: %v", err)
+	}
+	if _, _, err := Histogram(c, 2); err == nil || !strings.Contains(err.Error(), "no histogram") {
+		t.Fatalf("Histogram complex: %v", err)
+	}
+}