def transformBelowValue(requestContext, seriesList, valueLimit, newValue):
    """
    Takes one metric or a wildcard seriesList.

    For every point below (valueLimit), replace it with (newValue). Does nothing
    to NULLs
    """

    for series in seriesList:
        series.tags['transformBelowValue'] = valueLimit
        series.tags['transformBelowValueNewValue'] = newValue
        series.name = "transformBelowValue(%s,%g,%g)" % (series.name, valueLimit, newValue)
        series.pathExpression = series.name
        values = [newValue if ( v is not None and v < valueLimit ) else v for v in series]
        series[:len(series)] = values
    return seriesList