---
title: "lgdelta"
slug: "lgdelta"
updated: 2023-03-20T12:46:57Z
published: 2023-03-20T12:46:57Z
canonical: "docs.datajet.app/lgdelta"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.datajet.app/llms.txt
> Use this file to discover all available pages before exploring further.

# 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

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

![](blob:https://datajetsoftware.atlassian.net/50f5b809-5007-4b9a-be74-3704af4b6788#media-blob-url=true&id=5d1cda29-583b-4205-8ebd-81596156845b&collection=contentId-489357347&contextId=489357347&height=500&width=377&alt=)

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/image-1679315606704.png)

## Parameters

## 

![](blob:https://datajetsoftware.atlassian.net/e49ab35e-d8a4-471a-bf19-8528563e40d6#media-blob-url=true&id=5d7603f8-cedb-4fb7-b287-fa263ba274bc&collection=contentId-489357347&contextId=489357347&height=245&width=919&alt=)

| 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](/v1/docs/postfunction-log) [](https://datajetsoftware.atlassian.net/wiki/spaces/ED/pages/488898575)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

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/image-1679316009738.png)

![](https://cdn.document360.io/73b6469b-c1e4-47e9-aa65-986c8ebd17ca/Images/Documentation/image-1679316019811.png)