Add histogram creation.

src/__init__.py

@@ -971,6 +971,49 @@ class Table:
 
 
 
+def string_histogram(iterable, min_value=None, max_value=None, bin_count=20, width=75,
+        use_unicode=True):
+    if min_value is None or max_value is None:
+        iterable = list(iterable)
+        min_value = min(iterable)
+        max_value = max(iterable)
+
+    bin_width = (max_value - min_value)/bin_count
+    bins = [0 for i in range(bin_count)]
+
+    from math import floor, ceil
+    for value in iterable:
+        bin_nr = int(floor((value-min_value)/bin_width))
+        if 0 <= bin_nr < bin_count:
+            bins[bin_nr] += 1
+        else:
+            from warnings import warn
+            warn("string_histogram: out-of-bounds value ignored")
+
+    if use_unicode:
+        def format_bar(cnt):
+            scaled = cnt*width/max_count
+            full = int(floor(scaled))
+            eighths = int(ceil((scaled-full)*8))
+            if eighths:
+                return full*unichr(0x2588) + unichr(0x2588+(8-eighths))
+            else:
+                return full*unichr(0x2588)
+    else:
+        def format_bar(cnt):
+            return int(ceil(cnt*width/max_count))*"#"
+
+    max_count = max(bins)
+    total_count = sum(bins)
+    return "\n".join("%9g (%9d:%3.0f %%) : %s" % (
+        min_value+bin_nr*bin_width, 
+        bin_value,
+        bin_value/total_count*100,
+        format_bar(bin_value))
+        for bin_nr, bin_value in enumerate(bins))
+
+            
+        
 
 # command line interfaces -----------------------------------------------------
 class CPyUserInterface(object):