# periodOverPeriodPercentDifference


The `periodOverPeriodPercentDifference` function calculates the percent difference of a measure over two different time periods as specified by the period granularity and offset. Unlike percentDifference, this function uses a date-based offset instead of a fixed sized offset. This ensures only the correct dates are compared, even if data points are missing in the dataset.

## Syntax


```
periodOverPeriodPercentDifference(
	measure, 
	date, 
	period, 
	offset)
```

## Arguments


 *measure*   
An aggregated measure that you want to see the difference for.

 *date*   
The date dimension over which you're computing periodOverPeriod calculations.

 *period*   
(Optional) The time period across which you're computing the computation. Granularity of `YEAR` means `YearToDate` computation, `Quarter` means `QuarterToDate`, and so on. Valid granularities include `YEAR`, `QUARTER`, `MONTH`, `WEEK`, `DAY`, `HOUR`, `MINUTE`, and `SECONDS`.  
This argument defaults to the granularity of the visual aggregation

 *offset*   
(Optional) The offset can a positive or negative integer representing the prior time period (specified by period) that you want to compare against. For instance, period of a quarter with offset 1 means comparing against the previous quarter.  
This argument default value is 1.

## Example


The following example calculates the month over month percent difference in sales with the visual dimension granularity and default offset of 1.

```
periodOverPeriodPercentDifference(sum(Sales),{Order Date})
```

The following example calculates the month over month percent difference in sales with a fixed granularity of `MONTH` and fixed offset of 1.

```
periodOverPeriodPercentDifference(sum(Sales), {Order Date}, MONTH, 1)
```

![\[This is an image of the return of the example calculation.\]](http://docs.amazonaws.cn/en_us/quick/latest/userguide/images/MonthOverMonthPercentDifference.png)