Adding median as aggregation method.

README.md

@@ -38,7 +38,7 @@ Options:
   --aggregationMethod=AGGREGATIONMETHOD
                         The consolidation function to fetch from on input and
                         aggregationMethod to set on output. One of: average,
-                        last, max, min, avg_zero, absmax, absmin
+                        last, max, min, avg_zero, absmax, absmin, median
   --destinationPath=DESTINATIONPATH
                         Path to place created whisper file. Defaults to the
                         RRD file's source path.
@@ -66,7 +66,7 @@ Options:
   --xFilesFactor=XFILESFACTOR
   --aggregationMethod=AGGREGATIONMETHOD
                         Function to use when aggregating values (average, sum,
-                        last, max, min, avg_zero, absmax, absmin)
+                        last, max, min, avg_zero, absmax, absmin, median)
   --overwrite
   --estimate            Don't create a whisper file, estimate storage requirements based on archive definitions
 ```
@@ -170,7 +170,7 @@ Options:
                         Change the xFilesFactor
   --aggregationMethod=AGGREGATIONMETHOD
                         Change the aggregation function (average, sum, last,
-                        max, min, avg_zero, absmax, absmin)
+                        max, min, avg_zero, absmax, absmin, median)
   --force               Perform a destructive change
   --newfile=NEWFILE     Create a new database file without removing the
                         existing one
@@ -185,7 +185,7 @@ whisper-set-aggregation-method.py
 Change the aggregation method of an existing whisper file.
 
 ```
-Usage: whisper-set-aggregation-method.py path <average|sum|last|max|min|avg_zero|absmax|absmin>
+Usage: whisper-set-aggregation-method.py path <average|sum|last|max|min|avg_zero|absmax|absmin|median>
 
 Options:
   -h, --help  show this help message and exit

bin/rrd2whisper.py

@@ -28,6 +28,8 @@
 aggregationMethods.remove('absmax')
 # RRD doesn't have a 'absmin' type
 aggregationMethods.remove('absmin')
+# RRD doesn't have a 'median' type
+aggregationMethods.remove('median')
 
 option_parser = optparse.OptionParser(usage='''%prog rrd_path''')
 option_parser.add_option(

test_whisper.py

@@ -228,6 +228,10 @@ def test_aggregate(self):
         self.assertEqual(whisper.aggregate('absmin', [-3, -2, 1, 2]), 1)
         # absmin with negative min
         self.assertEqual(whisper.aggregate('absmin', [-2, -1, 2, 3]), -1)
+        # median with odd number of values
+        self.assertEqual(whisper.aggregate('median', [0, 14, 2, 3, 3]), 3)
+        # median with even number of values
+        self.assertEqual(whisper.aggregate('median', [10, 0, 6, 5]), 5.5)
 
         with AssertRaisesException(
                 whisper.InvalidAggregationMethod(