code: def logarithm(requestContext, seriesList, base=10):
      
      results = []
      for series in seriesList:
          newValues = []
          for val in series:
              if val is None:
                  newValues.append(None)
              elif val <= 0:
                  newValues.append(None)
              else:
                  newValues.append(math.log(val, base))
          newName = "log(%s, %s)" % (series.name, base)
          newSeries = TimeSeries(newName, series.start, series.end, series.step,
                                 newValues)
          newSeries.pathExpression = newName
          results.append(newSeries)
      return results
docs: Takes one metric or a wildcard seriesList, a base, and draws the y-axis in
      logarithmic format. If base is omitted, the function defaults to base 10.
  
      Example::
  
          &target=log(carbon.agents.hostname.avgUpdateTime,2)