Add horizontal_hist function

Author: duboviy

hist.py

@@ -0,0 +1,41 @@
+""" Horizontal histogram plotting function. """
+
+from __future__ import absolute_import
+import matplotlib.pyplot as plt
+import numpy as np
+
+
+def horizontal_hist(items, title=None, axis_label=None, color=None, height=10, width=20, reverse=False):
+    """
+    Plots a histogram of values and frequencies.
+
+    Arguments:
+        items (iterable[any])     => Example, [1, 2, 3, 1, 2]
+        title (Optional[str])     => Example, "Resulting histogram".
+        axis_label (Optional[str]) => Example, "y-axis".
+        color (Optional[str])     => Default: matplotlib's default plot color, a royal blue
+        height (Optional[int])    => Default: 10
+        width (Optional[int])     => Default: 20
+        reverse (Optional[bool])  => From top to bottom in order of decreasing frequency or not.
+
+    Returns:
+        None, however a matplotlib figure should be produced.
+    """
+
+    unique_items, item_counts = np.unique(items, return_counts=True)
+    item_counts, unique_items = zip(*sorted(zip(item_counts, unique_items), reverse=reverse))
+
+    pos = np.arange(len(unique_items)) + 0.5
+    plt.figure(figsize=(width, height))
+    plt.barh(pos, item_counts, align='center', color=color)
+    plt.yticks(pos, unique_items)
+    plt.xlabel('Frequency')
+    plt.ylabel(axis_label) if axis_label else None
+    plt.title(title) if title else None
+
+    plt.show()
+
+
+if __name__ == '__main__':
+    items = range(1, 10) * 100 + range(11, 20) * 50 + range(21, 30) * 25
+    horizontal_hist(items, title="Resulting histogram")