Median (Variable Length) [MedianVL]

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The Median (Variable Length) function determines the median value of a series with a variable number of bars. Parameters ------------------ Data          The data to evaluate. This is typically a field in a data series or a calculated value. Period        The number of bars of data to include in the sample, including the current value.                   For example, a period of 3 includes the current value and the two previous values. Maximum Period   The maximum value that Period can contain.                              Larger values require extra memory to be set aside for this function to be calculated. Note: An end point to the Period parameter can be simulated using the Lag function to obtain a previous value of this function. See the notes for the Lag function for more information. Function Value ------------------------ This function determines the median value of a data series within a given period. The median is the number in the middle of all of the values if the values were to be sorted. If an odd value is used for the period, the median will be an actual number from the series. If an even value is used, the median will be the average of the two middle values. If the data series does not have enough data to fill the period or it contains a null during the period, a null is returned. If the period is greater than the maximum period or negative, the value is not defined. If the period contains a fractional number, only the integer portion will be used. As a result of finding the median, half of the values during the given period have a value equal to or greater than the median and half of the values have a value equal to or less than the median. The median is useful for obtaining an "average" value of a data series while practically removing the effects of outliers. Variable length functions can be used in association with other calculations, such as "Bars Since" functions, to determine values since an event occurred. For example, the following formula would return the median of the High field since the highest high in the last ten bars: MedianVL ( High, Add ( BarsSinceHigh ( High, 10 ) , 1 ) , 10)