Testing Class Material

hands_on_solutions/local_maxima/local_maxima.py

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+def find_maxima(x):
+    """Find local maxima of x.
+
+    Example:
+    >>> x = [1, 3, -2, 0, 2, 1]
+    >>> find_maxima(x)
+    [1, 4]
+
+    If in a local maximum several elements have the same value,
+    return the left-most index.
+    Example:
+    >>> x = [1, 2, 2, 1]
+    >>> find_maxima(x)
+    [1]
+
+    Input arguments:
+    x -- 1D list of real numbers
+
+    Output:
+    idx -- list of indices of the local maxima in x
+    """
+
+    idx = []
+    up = False
+    down = False
+    for i in range(len(x)):
+        if i == 0 or x[i-1] < x[i]:
+            up = True
+            up_idx = i
+        elif x[i-1] > x[i]:
+            up = False
+
+        # if x[i-1] == x[i], no change
+
+        if i+1 == len(x) or x[i+1] < x[i]:
+            down = True
+        elif x[i+1] > x[i]:
+            down = False
+
+        if up and down:
+            idx.append(up_idx)
+
+    return idx
+

hands_on_solutions/local_maxima/test_local_maxima.py

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+from local_maxima import find_maxima
+
+
+def test_find_maxima():
+    values = [1, 3, -2, 0, 2, 1]
+    expected = [1, 4]
+    maxima = find_maxima(values)
+    assert maxima == expected
+
+
+def test_find_maxima_edges():
+    values = [4, 2, 1, 3, 1, 5]
+    expected = [0, 3, 5]
+    maxima = find_maxima(values)
+    assert maxima == expected
+
+
+def test_find_maxima_empty():
+    values = []
+    expected = []
+    maxima = find_maxima(values)
+    assert maxima == expected
+
+
+def test_find_maxima_plateau():
+    values = [1, 2, 2, 1]
+    expected = [1]
+    maxima = find_maxima(values)
+    assert maxima == expected
+
+
+def test_find_maxima_not_a_plateau():
+    values = [1, 2, 2, 3, 1]
+    expected = [3]
+    maxima = find_maxima(values)
+    assert maxima == expected