fix: Allow Binseg to hit minsize bounds for segments (#249)

* storing work to fix precommit and docs

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* test: compare to the explicit results rather than lenght

* style: typos in comment

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Charles T <charles@doffy.net>

src/ruptures/detection/binseg.py

@@ -90,7 +90,7 @@ def single_bkp(self, start, end):
             return None, 0
         gain_list = list()
         for bkp in range(start, end, self.jump):
-            if bkp - start > self.min_size and end - bkp > self.min_size:
+            if bkp - start >= self.min_size and end - bkp >= self.min_size:
                 gain = (
                     segment_cost
                     - self.cost.error(start, bkp)

tests/test_detection.py

@@ -357,6 +357,17 @@ def test_model_small_signal(signal_bkps_5D_n10, algo, model):
     )
 
 
+@pytest.mark.parametrize(
+    "model",
+    ["l1", "l2", "ar", "normal", "rbf", "rank", "mahalanobis"],
+)
+def test_binseg_min_size(signal_bkps_5D_n10, model):
+    signal, _ = signal_bkps_5D_n10
+
+    c_bkps = Binseg(model=model, min_size=5, jump=1).fit_predict(signal, n_bkps=1)
+    assert all([a == b for a, b in zip(c_bkps, [5, 10])])
+
+
 @pytest.mark.parametrize(
     "model", ["l1", "l2", "ar", "normal", "rbf", "rank", "mahalanobis"]
 )
@@ -368,6 +379,9 @@ def test_model_small_signal_dynp(signal_bkps_5D_n10, model):
         Dynp(model=model, min_size=9, jump=2).fit_predict(signal, 2)
     with pytest.raises(BadSegmentationParameters):
         Dynp(model=model, min_size=11, jump=2).fit_predict(signal, 2)
+    # Test if it can find the single eligible break point compatible with min_size
+    c_bkps = Dynp(model=model, min_size=5, jump=1).fit_predict(signal, 1)
+    assert all([a == b for a, b in zip(c_bkps, [5, 10])])
 
 
 @pytest.mark.parametrize(