lgdelta

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

Calculates the natural log for each row (log)
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
Dimensions	Discrete field(s). All fields must come from the same table.
Name	Name to be displayed as Column Header in result grid
Measure	The 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.
Function	COUNT / SUM / AVG / MIN / MAX / STDEV
Post	lgdelta
Value	Optional. 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.
Axis	0 / 1. Y-Axis to use when plotting graph. Default = 0
Plot	Y / N. Specifies whether measure’s output column should be plotted on graph. Default = Y
Resolve	Optional. Resolve level for the measure. If blank, Resolve = Dimension Table
Series Type	Default / Bar / Stacked Bar / Line / Spline / RangeLow / RangeHigh / CSLow / CSHigh / CSOpen / CSClose Determines the graph style for the measure.
Popup	Default / 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:=

lgdelta

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

Purpose

Calculation

Sample Result

Parameters

Usage Notes

Example

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