feat: add Anchored RSI to the momentum oscillators family (#144)

Cumulative Relative Strength Index whose averaging begins at a runtime-chosen anchor bar (set_anchor), the momentum counterpart to Anchored VWAP. Scalar f64 input, 0..=100 output; wired through core, Python, Node and WASM bindings, fuzz, benches, tests and docs. Indicator count 289 -> 290.

bindings/python/tests/test_known_values.py

@@ -66,6 +66,14 @@ def test_rsi_wilder_textbook_first_value():
     assert math.isclose(out[14], 70.464, abs_tol=0.05)
 
 
+def test_anchored_rsi_cumulative_reference():
+    """Cumulative anchored RSI: 10 -> 11 (+1) -> 9 (-2) -> 12 (+3)."""
+    out = ta.AnchoredRSI().batch(np.array([10.0, 11.0, 9.0, 12.0]))
+    assert math.isclose(out[1], 100.0, abs_tol=1e-9)
+    assert math.isclose(out[2], 100.0 - 100.0 / 1.5, abs_tol=1e-6)
+    assert math.isclose(out[3], 100.0 - 100.0 / 3.0, abs_tol=1e-6)
+
+
 def test_inertia_constant_rvi_passes_through_linreg():
     # Every bar identical (open, high, low, close) = (10, 11, 9, 10.5):
     # RVI = (c-o) / (h-l) = 0.5 / 2 = 0.25 every bar. LinReg of a constant

bindings/python/tests/test_lifecycle.py

@@ -12,6 +12,7 @@ SCALAR_INDICATORS = [
     (ta.EMA, (14,)),
     (ta.WMA, (14,)),
     (ta.RSI, (14,)),
+    (ta.AnchoredRSI, ()),
     (ta.MACD, ()),
     (ta.BollingerBands, ()),
 ]
@@ -42,6 +43,7 @@ def test_reset_returns_to_initial_state(cls, args):
         (ta.EMA, (14,), 14),
         (ta.WMA, (14,), 14),
         (ta.RSI, (14,), 15),
+        (ta.AnchoredRSI, (), 2),
         (ta.BollingerBands, (20, 2.0), 20),
     ],
 )

bindings/python/tests/test_new_indicators.py

@@ -1193,6 +1193,42 @@ def test_anchored_vwap_set_anchor_clears_window():
     assert v == pytest.approx(100.0)
 
 
+def test_anchored_rsi_reference():
+    # prices 10 -> 11 (+1) -> 9 (-2) -> 12 (+3); cumulative anchored RSI.
+    # bar2: sum_gain=1, sum_loss=2 -> rs=0.5 -> 100 - 100/1.5 = 33.3333
+    # bar3: sum_gain=4, sum_loss=2 -> rs=2.0 -> 100 - 100/3   = 66.6667
+    rsi = ta.AnchoredRSI()
+    out = rsi.batch(np.array([10.0, 11.0, 9.0, 12.0]))
+    assert np.isnan(out[0])
+    assert out[1] == pytest.approx(100.0)
+    assert out[2] == pytest.approx(33.333333, abs=1e-4)
+    assert out[3] == pytest.approx(66.666666, abs=1e-4)
+
+
+def test_anchored_rsi_set_anchor_clears_window():
+    # Downtrend reads 0; after re-anchor an uptrend must read a fresh 100.
+    rsi = ta.AnchoredRSI()
+    for p in (20.0, 19.0, 18.0, 17.0):
+        rsi.update(p)
+    assert rsi.is_ready()
+    assert rsi.value == pytest.approx(0.0)
+    rsi.set_anchor()
+    assert rsi.update(50.0) is None
+    assert rsi.update(51.0) == pytest.approx(100.0)
+
+
+def test_anchored_rsi_streaming_matches_batch():
+    prices = np.array([100.0 + np.sin(i * 0.4) * 8.0 for i in range(60)])
+    batched = ta.AnchoredRSI().batch(prices)
+    streamer = ta.AnchoredRSI()
+    streamed = [streamer.update(float(p)) for p in prices]
+    for b, s in zip(batched, streamed):
+        if np.isnan(b):
+            assert s is None
+        else:
+            assert s == pytest.approx(b)
+
+
 def test_tsv_reference():
     # closes  = [10, 11, 13, 12, 14, 15]
     # volumes = [50, 100, 200, 150,  50, 200]