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      lgdelta
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      Contents

      lgdelta

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      Article summary

      Returns the difference between the natural logarithm for the current row and the natural logarithm for the previous row

      Purpose

      Use this function to: 

      • Calculate the change in logarithm

      Calculation

      1. Calculates the natural log for each row (log)
      2. Calculates the difference between the logs (lgdelta)

      lgdelta= log(RowX) - log(Row(X-1))

      RowX = value for current row
      Row(X+1) = value for next row 
      log(RowX) = natural log for current row
      log(Row(X-1)= natural log for previous row

      Sample Result

       

      Parameters

      Parameter`Description
      DimensionsDiscrete field(s).    All fields must come from the same table.
      NameName to be displayed as Column Header in result grid
      MeasureThe field to be used in the post-function calculation.
      • Must be numeric if Function is anything other than COUNT.
      • Must come from same table as DIMENSIONS.
      • Supports Discrete or Continuous DataTypes.
      FunctionCOUNT / SUM / AVG / MIN / MAX / STDEV
      Postlgdelta
      ValueOptional.   Filter to apply when evaluating FUNCTION.   Only records in the Filter Recordset will be included in the Function and Post-Function calculations.
      Must come from same table as DIMENSION/MEASURE or be linked to the Dimension table.
      Axis0 / 1.    Y-Axis to use when plotting graph.     Default = 0
      PlotY / N.   Specifies whether measure’s output column should be plotted on graph.  Default = Y
      ResolveOptional.   Resolve level for the measure.   If blank, Resolve = Dimension Table
      Series TypeDefault / Bar / Stacked Bar / Line / Spline / RangeLow / RangeHigh / CSLow / CSHigh / CSOpen / CSClose
      Determines the graph style for the measure.
      PopupDefault / None / Extended
      Prefix$ / £ / E / %

      Usage Notes

      See log  for details on calculating natural logarithms.

      Example

      NOTE: Measures 1 and 2 are included purely for illustration. It is not necessary to include these measures for the calculation to work.


      Dimension (s):  [transactions].[product_group], [transactions].[yearmonth]

      Measure 1

      • Name: = Count
      • Measure:  = transactions.cid
      • Function: = count
      • Post: =
      • Value: =
      • Axis: =0
      • Plot:= N
      • Resolve:=
      • Series Type:=Default
      • Popup:=Default
      • Prefix:=


      Measure 2

      • Name: = Log
      • Measure:  = transactions.cid
      • Function: = count
      • Post: =log
      • Value: =
      • Axis: =0
      • Plot:=Y
      • Resolve:=
      • Series Type:=Default
      • Popup:=Default
      • Prefix:=


      Measure 3

      • Name: = lgdelta
      • Measure:  = transactions.cid
      • Function: = count
      • Post: =lgdelta
      • Value: =
      • Axis: =0
      • Plot:=Y
      • Resolve:=
      • Series Type:=Default
      • Popup:=Default
      • Prefix:=


      Example use: Using lgdelta to calculate the difference in log values



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