def integral(requestContext, seriesList):
    results = []
    for series in seriesList:
        newValues = []
        current = 0.0
        for val in series:
            if val is None:
                newValues.append(None)
            else:
                current += val
                newValues.append(current)
        newName = "integral(%s)" % series.name
        newSeries = TimeSeries(newName, series.start, series.end, series.step,
                               newValues)
        newSeries.pathExpression = newName
        results.append(newSeries)
    return results