Include the right edge in find_local_peaks window

docs/changes.rst

@@ -80,6 +80,9 @@ Unreleased
 **Use only beat annotations in ann2rr**
   ``ann2rr`` now computes intervals between beat (QRS) annotations only, as the WFDB ``ann2rr`` program does, so rhythm changes, comments and other non-beat annotations no longer split an RR interval in two. The first interval is still measured from the start of the record. To include all annotations as before, pass ``all_annotations=True`` (the equivalent of ``ann2rr -A``).
 
+**Include the right edge of the window in find_local_peaks**
+  ``find_local_peaks`` now compares each sample with ``radius`` samples on both sides, as documented, and is about 3 times faster. The sample ``radius`` positions to the right, and the last sample of the signal, used to be left out. ``XQRS`` uses ``find_local_peaks`` to find candidate peaks, so its detections may change slightly.
+
 Version 4.3.1 (Feb 2026)
 -----------------------------
 

src/wfdb/processing/peaks.py

@@ -59,7 +59,9 @@ def find_local_peaks(sig, radius):
 
     A sample is a local peak if it is the largest value within the <radius> samples on
     its left and right. In cases where it shares the max value with nearby samples, the
-    middle sample is classified as the local peak.
+    first of these samples is classified as the local peak. The search then continues
+    <radius> samples later, so a flat top that is wider than <radius> samples gives a
+    peak every <radius> samples along it.
 
     Parameters
     ----------
@@ -75,28 +77,15 @@ def find_local_peaks(sig, radius):
 
     """
     # TODO: Fix flat mountain scenarios.
+    sig = np.asarray(sig)
     if np.min(sig) == np.max(sig):
         return np.empty(0)
 
     peak_inds = []
 
     i = 0
-    while i < radius + 1:
-        if sig[i] == max(sig[: i + radius]):
-            peak_inds.append(i)
-            i += radius
-        else:
-            i += 1
-
-    while i < len(sig):
-        if sig[i] == max(sig[i - radius : i + radius]):
-            peak_inds.append(i)
-            i += radius
-        else:
-            i += 1
-
     while i < len(sig):
-        if sig[i] == max(sig[i - radius :]):
+        if sig[i] == sig[max(0, i - radius) : i + radius + 1].max():
             peak_inds.append(i)
             i += radius
         else:

tests/test_processing.py

@@ -105,6 +105,17 @@ def test_find_peaks_empty(self):
         assert hp.shape == (0,)
         assert sp.shape == (0,)
 
+    def test_find_local_peaks(self):
+        # the sample `radius` positions to the right is part of the window
+        x = np.array([0, 1, 2, 3, 2, 1, 0], dtype=float)
+        assert np.array_equal(processing.find_local_peaks(x, 1), [3])
+        x = np.array([0, 1, 3, 2, 10, 5, 1, 0], dtype=float)
+        assert np.array_equal(processing.find_local_peaks(x, 2), [4])
+
+    def test_find_local_peaks_list(self):
+        """A list works as well as an array."""
+        assert processing.find_local_peaks([0, 1, 2, 3, 2, 1, 0], 1).tolist() == [3]
+
     def test_gqrs(self):
         record = wfdb.rdrecord(
             "sample-data/100",