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[hydralien <question72090@xxxxxxxxxxxxxxxxxxxxx>]

Question #72090 on Graphite changed:
https://answers.launchpad.net/graphite/+question/72090

hydralien proposed the following answer:
Hi,

I just faced the same problem and found this ticket. From the attached
bug I found out that changes are done and merged, so I tried the trunk
code. So the function works, but I think in a rather weird way. Meaning,
it does what it's designed for, keeping last value till the new value
found, but it makes plot staircased which is I believe not the desired
behavior. Would be nice if Graphite could draw a direct line from
previous point to the current one, pretending a set of averaged values
between those points.

Actually, I've added following diff to the functions to do what I need.
Sorry if it looks ugly - this is my first Python code.

=== modified file 'webapp/web/render/functions.py'
--- webapp/web/render/functions.py      2009-08-07 18:05:06 +0000
+++ webapp/web/render/functions.py      2009-08-13 14:25:55 +0000
@@ -22,6 +22,12 @@
   if not safeValues: return None
   return sum(safeValues)

+def safeSub(a,b):
+  if a is None and b is None: return None
+  if a is None: return None
+  if b is None: return a
+  return a - b
+
 def safeDiff(values):
   safeValues = [v for v in values if v is not None]
   if not safeValues: return None
@@ -106,6 +112,27 @@
       series[i] = value
   return seriesList

+def averageLastValue(seriesList):
+  for series in seriesList:
+    series.name = "averageLastValue(%s)" % (series.name)
+    i = 0
+    addition = None
+    series_length = len(series)
+    while i < series_length:
+      value = series[i]
+      if (value is None) and (addition is None) and (i > 0) and (series[i-1] is not None):
+        j = i + 1
+        while (j < series_length) and (addition is None):
+          if series[j] is not None:
+            addition = safeDiv(safeSub(series[j], series[i-1]), j - i)
+          j += 1
+      if (value is None):
+        series[i] = safeSum([series[i-1], addition])
+      else:
+        addition = None
+      i += 1
+  return seriesList
+
 def asPercent(seriesList1,seriesList2orNumber):
   assert len(seriesList1) == 1, "asPercent series arguments must reference *exactly* 1 series"
   series1 = seriesList1[0]
@@ -318,4 +345,5 @@
   'lastAbove' : lastAbove,
   'highestMean' : highestMean,
   'highestLast' : highestLast,
+  'averageLastValue' : averageLastValue,
 }

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