**Summary**

In an iDashboards expression, you can use math functions.

- Math.abs(y1) returns the absolute value of y1
- Math.round(y1) rounds up if the fractional-part of y1 >= 0.5 and rounds down if the fractional part of y1 < 0.5
- Math.ceil(y1) rounds up to the nearest whole number
- Math.floor(y1) rounds down to the nearest whole number

*Note: case matters. Make sure the function (abs, round…) are in lowercase.*

**Real-world Example**

If a driver leaves a location at a given start time and arrives at a destination at a given end time calculate the how many hours a driver was on the road.

Assign y1 to the start date

Assign y2 to the end date

For y3 copy in the expression below:

// number of milliseconds in one hour

var ONE_HOUR = 1000 * 60 * 60

// convert dates to milliseconds

var startDate_ms = y1.getTime()

var endDate_ms = y2.getTime()

// Calculate the difference

var difference_ms = Math.abs(endDate_ms - startDate_ms)

// convert back to hours

Math.round(difference_ms/ONE_HOUR)

Here is some sample data to see what the expression would return:

For more functions you can use in the Java math library, visit **http://docs.oracle.com/javase/6/docs/api/java/lang/Math.html**

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