periodToDateMinOverTime
The periodToDateMinOverTime function calculates the minimum of a measure
			for a given time granularity (for instance, a quarter) up to a point in time.
Syntax
periodToDateMinOverTime( measure, dateTime, period)
Arguments
- measure
- 
						An aggregated measure that you want to do the calculation 
- dateTime
- 
						The date dimension over which you're computing PeriodOverTime calculations. 
- period
- 
						(Optional) The time period across which you're computing the computation. Granularity of YEARmeansYearToDatecomputation,QuartermeansQuarterToDate, and so on. Valid granularities includeYEAR,QUARTER,MONTH,WEEK,DAY,HOUR,MINUTE, andSECONDS.The default value is the visual's date dimension granularity. 
Example
The following example calculates the minimum fare amount month over month.
periodToDateMinOverTime(min({fare_amount}), pickupDatetime, MONTH)
