There are multiple tools in the GeoAnalytics Tools toolbox that allow you to apply an expression.

- Buffer expressions in Create Buffers
- Buffer expressions in Reconstruct Tracks
- Join conditions in Join Features
- Incident conditions in Detect Incidents
- Calculating field values in Calculate Field

The GeoAnalytics Tools that use expressions have different usages, as well limitations on which expressions can be applied. At 10.6.1, all expressions used in ArcGIS GeoAnalytics Server support Arcade.

Learn more about Arcade Functions

## Expressions in Detect Incidents

Expressions are used in the Detect Incidents tool to specify start and end conditions for incidents. A Detect Incidents condition must always result in true or false. Use a condition to check if a feature should be included in an incident. The conditions are tested against each feature to determine which features are incidents. Calculations are performed when the analysis runs on your ArcGIS GeoAnalytics Server. Expression examples that can be used are included in the sections below.

## Mathematical operator and function examples

Expressions are able to mathematically process numbers. The following table shows a sample of available operations.

Learn more about mathematical operations and functions available in Arcade

Operator | Explanation | Example | Result |
---|---|---|---|

a + b | a plus b. | fieldname contains a value of 1.5 $feature["fieldname"] + 2.5 | 4.0 |

a - b | a minus b. | fieldname contains a value of 3.3 $feature["fieldname"]- 2.2 | 1.1 |

a * b | a times b. | fieldname contains a value of 2.0 $feature["fieldname"] * 2.2 | 4.4 |

a / b | a divided by b. | fieldname contains a value of 4.0 $feature["fieldname"] / 1.25 | 3.2 |

abs( a ) | Returns the absolute (positive) value of a. | fieldname contains a value of -1.5 abs($feature["fieldname"]) | 1.5 |

log( a ) | Returns the natural logarithm (base E) of a. | fieldname contains a value of 1 log($feature["fieldname"]) | 0 |

sin( a ) | Returns the trigonometric sine of a. The input is assumed to be an angle in radians. | fieldname contains a value of 1.5707 sin($feature["fieldname"]) | 1 |

cos( a ) | Returns the trigonometric cosine of a. The input is assumed to be an angle in radians. | fieldname contains a value of 0 cos($feature["fieldname"]) | 1 |

tan( a ) | Returns the tangent of a. The input is assumed to be an angle in radians. | fieldname contains a value of 0 tan($feature["fieldname"]) | 0 |

sqrt( a ) | Returns the square root of a. | fieldname contains a value of 9 sqrt($feature["fieldname"]) | 3 |

min( a, b ) | Returns the lowest-valued number between a and b. | fieldname contains a value of 1.5, and a value of -3 min($feature["fieldname"], -3) | -3 |

max( a, b ) | Returns the highest-valued number between a or b. | fieldname1 contains a value of 1.5, and fieldname2 contains a value of -3 max($feature["fieldname1"], $feature["fieldname2"]) | 1.5 |

constrain(<value>,<low>,<high>) | Returns the input value if it's within the constraining bounds. If the input value is less than the low value, it returns the low value. If the input value is greater than the high value, it returns the high value. | constrain($feature["distance"], 0, 10) constrain($feature['Store dist'], 6, distance) | Returns 0 if distance is less than 0, 10 if distance is greater than 10, and distance otherwise. Returns 6 if Store dist is less than 6, distance if Store dist is greater than distance, and Store dist otherwise. |

Multiplication example for a condition detecting an incident.

`$feature["Distance"] * 2 > 50`

## Text function examples

Detect Incidents expressions are able to process text. The following table shows a sample of available operations.

Learn more about text functions available in Arcade

Operator | Explanation | Example | Result |
---|---|---|---|

concatenate( <values>, <separator>) | Concatenates values together and returns a string. - values—An array of string values to concatenate.
- separator ( optional)—A separator to use for concatenation if the values parameter is an array, or a string to concatenate if a single value is provided for the first parameter. If not provided, it will be empty.
| fieldname contains a value of GeoAnalytics Concatenate ([$features["fieldname"], "is", "great!"], ' ') | GeoAnalytics is great! |

find(<searchText>, <text>, <startPos>) | Finds a string within a string. Wildcards are not supported. - searchText—The substring to search for.
- text—The text to search.
- startPos (optional)—The zero-based index of the location in the string to search from.
| fieldname1 contains a value of 14NorthStreet and fieldname2 contains a value of North find($feature["fieldname2"], $feature["fieldname1"]) | 2 |

lower(<value>) | Makes a string lowercase. - value—The string to be made lowercase.
| fieldname contains a value of GEOANALYTICS lower($feature["fieldname"]) | geoanalytics |

Text example using find and lower.

`find(("north"), lower("146NorthStreet")) == 2`

## Date function examples

You can use Detect Incidents from expressions that use dates. The following table shows a sample of available operations.

Learn more about date functions available in Arcade

In Arcade, month values range from 0 (January) to 11 (December), days from 1 to 31, hours from 0 (12:00 a.m.) to 23 (11:00 p.m.), minutes and seconds from 0 to 59, and milliseconds from 0 to 999. Arcade dates return time values in the location of your GeoAnalytics Server.

Operator | Explanation | Example | Result |
---|---|---|---|

date( <value>, <month>, <day>, <hour>, <minute>) | Parses a value or set of values into a date string. - value(optional)— Either the number of milliseconds since January 1, 1970 UTC or a number representing a year. If a year is specified, the month and day must also be provided in subsequent parameters. This value may also be a date string or an ISO 8601 string to be converted into a date.
- month (optional)—The month (0–11), where 0 is January and 11 is December.
- day (optional)—The day of the month (1–31).
- hour (optional)—The hour of the day (0–23).
- minute (optional)—The minute of the hour (0–59).
- second (optional)—The second of the minute (0–59).
- millisecond (optional)—The millisecond of the second (0–999).
| fieldname contains a value of 1476987783555 Example 1: Date($features["fieldname"]) Example 2: Date(2017,0,14,0) Example 3: Date() | Example 1: 20 Oct 2016 11:23:03 am Example 2: 14 Jan 2017 12:00:00 am Example 3: Returns the current time |

DateDiff(<date1>, <date2>, <units>) | Subtracts two dates, and returns the difference in the specified units. - date1—The date value from which to subtract a second date.
- date2—The date value to subtract from the first given date.
- startpos (optional)—The units in which to return the difference of the two given dates. The supported unit types include milliseconds, seconds, minutes, hours, days, months, and years. The default value is milliseconds.
| Example 1: DateDiff(Date(2017,1,14,0), Date()) Example 2: DateDiff(Date(2017,1,14,0), Date(), "Years") | Result will vary depending on when you run this command. Example 1: -20532129137 Example 2: -0.6546783768647119 |

Year(<dateValue>) | Returns the year of the given date. - value—A date value from which to get the year.
| Example 1: fieldname is a field of type Date with a value of 09 Oct 2017 04:30:43 pm Year($feature["fieldname"]) Example 2: fieldname is a string field formatted as an ISO 8601 string with a value of 2012-09-27 | Example 1: 2017 Example 2: 2012 |

## Conditional operators

Conditional statements can use the following operators:

Operator | Explanation | Example | Results |
---|---|---|---|

a > b a < b | a is greater than b a is less than b | 10 > 2 | False |

a >= b a <= b | a is greater than or equal to b a is less than or equal to b | abs(-10) >= 10 | True |

a != b | a is not equal to b | abs(-3) != -3 | True |

a == b | a is equal to b | abs(-5) == 5 | True |

<condition1> || <condition2> | Condition 1 or condition 2 is met. | (abs(-5) == 5) || (10 < 2) | True |

<condition1> && <condition2> | Condition 1 and condition 2 are met. | (abs(-5) == 5) && (10 < 2) | False |

## Logical operator examples

In addition to the conditional operators, more advanced logical operators can be used with Detect Incidents.

Learn more about logical functions available in Arcade

Function | Explanation | Example | Result |
---|---|---|---|

iff(<condition>,<true value>,<false value>) | Returns one value if a condition evaluates to true, and another value if the condition evaluates to false. <true value> and <false value> can be the following: - A numeric field. If there is a space in the field name, use square brackets.
- A number.
- A function.
| iff($feature["field1"] > $feature["field2"], $feature["field1"], 0) iff($feature["field1"] > $feature["field2"], iff($feature["field2"] = 0, $feature["field3"], $feature["field4"]), 0) | Returns field1 if field1 is greater than field2, and 0 otherwise. Returns the result of the second iff function if field1 is greater than field2, and 0 otherwise. |

when(<expression1> , <result1> , <expression2> , <result2> , ... , <expressionN> , <resultN>, <default>) | Evaluates a series of expressions in turn, until one evaluates to true. - expression—An expression.
- result—Can be a number or field.
- default—An optional value if none of the expressions match.
| when(($feature["field1"] + 10) > 1, 1,($feature["field2"] + 10) > 2 , 2, $feature["field3"]) | If field1 + 10 is greater than 1, it returns 1. If not, it checks if field2 + 10 is greater than 2. If it is, it returns 2. If not, it returns field3. |

decode(<conditional val> , <case1> , <result1>, <case2>, <result2>, ... <caseN>, <resultN>, <defaultValue> ) | The decode function evaluates an expression and compares its value with subsequent parameters. If the expression matches, it returns the next parameter value. If none match, there is the option for the last parameter to be a default return value. - conditional val—Can be a field or an expression.
- case—A value to be compared to the conditional val.
- result—The result if the corresponding case matches the conditional val.
- defaultValue—An optional value if no other values are true.
| decode($feature["field1"] + 3 , $feature["field1"], 1, $feature["field2"], 2, 0) | Compares equality between the conditional val field1 + 3 and case1 field1. If true, it returns 1. If false, it compares the equality between field1 + 3 and field2. If true, it returns 2; otherwise, it returns 0. |

## Track-aware examples

In addition, some GeoAnalytics Tools, such as Detect Incidents and Calculate Field, can use track-aware equations in Arcade.

Function | Explanation | Example | Result | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

$track.field["fieldname"].history(<value1>) | Returns an array of values in the given field for the specified time index. - A positive number returns an array starting from the given index until the current feature.
- A negative number returns the current time step and the preceding <value1> - 1 time step values.
| MyField has sequentially ordered values of [10, 20, 30, 40, 50, 60, 70, 80]. The value 10 is at index 0, and the value 80 is at index 7. Expressions are evaluated at each index, and examples outline the index being used for the examples. n represents the number of features in the sequence, and k represents the index being evaluated. Example 1:$track.field["MyField"].history(3)) Example 2:$track.field["MyField"].history(-3) Example 3:mean($track.field["MyField"].history(-2)) Example 4:$track.field["MyField"].history(-3)[0] | When example 1 is evaluated at index k, it will return an array of values at index 3 through k. If you evaluate at index 6 (70), an array of the values at index [3, 4, 5, 6] is returned so that the array is [40, 50, 60, 70]. Example 2 returns an array of values calculated as index k minus the given value minus 1 (k-2). If this is evaluated at index 6 (value = 70), the values of k-2, k-1, and k are returned [50, 60, 70]. Example 3 returns the mean of the values at index k-1 and k. If you evaluate this at index 4 (value = 50), you will find the mean of value 50 (index 3) and value 60 (index 4), which equals 65. If you were to evaluate this at index 7, the result would be the mean of 70 and 80, which equals 75. Example 4 returns the first item (index 0) of the array created in example 2, which is 50. | ||||||||||||

$track.field["fieldname"].history(<value1>, <value2>) | Returns an array of values starting from index1 (<value1>) up to index2 (<value2>). | MyField has sequentially ordered values of [10, 20, 30, 40, 50, 60, 70, 80]. 10 is at index 0, and 80 is at index 7. For this example, expressions are evaluated at index 7 (80). Example 1:$track.field["MyField"].history(-3, -2)) Example 2:$track.field["MyField"].history(-5, -2)) | Example 1: [60] Example 2: [40, 50, 60] | ||||||||||||

$track.time.start | Calculates the start time of a track in milliseconds from epoch. | Using a track that starts on January 2, 2017 $track.time.start | 1483315200000 | ||||||||||||

$track.time.duration | Calculates the duration of a track in milliseconds from the start until the current time step. | Using a track that starts on January 2, 2017, and the current time is January 4, 2017. $track.time.duration | 172800000 | ||||||||||||

$track.time.current | Calculates the current time in a track. | Using a feature that occurs on January 3, 2017, at 9:00 a.m. $track.time.current | 1483434000000 | ||||||||||||

$track.index | Returns the time index of the feature being calculated. | Calculating this value on the first feature in a track. $track.index | 0 | ||||||||||||

$track.T(<value>, "<units>") | Returns the feature time plus the time created using the numeric <value> and given <units>. - value—The numeric value to add to the feature's time.
- units—The units of the numeric <value>. The supported unit types are milliseconds, seconds, minutes, hours, days, months, and years. The default value is milliseconds.
| Using a feature that is at January 2, 2017, at 2 p.m. Example 1: $track.T(1, "hours") Example 2: $track.T(-2, "days") | Example 1: Returns January 2 at 3 p.m.: 1483369200000 Example 2: Returns December 31st at 2 p.m.: 1483192800000 | ||||||||||||

$track.field["fieldname"].window(<value1>, <value2>) | Returns an array of values in the given field for the specified time index. The window function allows you to go forward and backward in time. The expression is evaluated at each feature in the track. - The current feature is at index 0.
- Positive values represent features that occur in the future, after the current value. For example, position 1 is the next value in the array.
- Negative numbers represent features that occurred in the past, before the previous feature. For example, -1 is the previous value in the array.
The window function is available at ArcGIS Enterprise 10.6.1. | MyField has sequentially ordered values of [10, 20, 30, 40, 50]. The expression is evaluated at each feature in the track. Results are returned inclusive of the start feature, and exclusive of the end feature. Example 1:$track.field["MyField"].window(-1,2) Example 2:$track.field["MyField"].window(-2,0)[0] Example 3:$track.field["MyField"].window(0,3)[2] | Example 1: When evaluated at each feature, the table shows the following results.
Example 2: When evaluated at index 2 (value is 30), it returns: 10. Example 3: When evaluated at index 2 (value is 30), it returns: 50. | ||||||||||||

$track.geometry.window(<value1>, <value2>) | Returns an array of values representing geometry for the specified time index. The window function allows you to go forward and backward in time. The expression is evaluated at each feature in the track. - The current feature is at index 0.
- Positive values represent features that occur in the future, after the current value. For example, position 1 is the next value in the array.
- Negative numbers represent features that occurred in the past, before the previous feature. For example, -1 is the previous value in the array.
The window function is available at ArcGIS Enterprise 10.6.1. | MyField has sequentially ordered values of [10, 20, 30, 40, 50]. The geometry of the features are [{x: 1, y: 1},{x: 2, y: 2} ,{x: null, y: null},{x: 4, y: 4}, {x: 5, y: 5}] The expression is evaluated at each feature in the track. Results are returned inclusive of the start feature, and exclusive of the end feature. Example 1:$track.geometry.window(-1,2) Example 2: $track.geometry.window(0,1)[0] on a polyline dataset Example 3: $track.geometry.window(0,1)[0] on a polygon dataset Example 4: Find the X value of the previous point $track.geometry.window(-1,0)[0]["x"] | Example 1: When evaluated at each feature, the table shows the following results.
Example 2: Polylines are returned in the following format: [{"paths":[[[-180,-22.88],[-177.6,-23.6]],[[180,-18.099999999999994],[179.7,-18.4],[179.4,-18.7],[178.9,-18.9],[178.5,-19.3],[178.2,-19.7],[178.4,-20],[178.8,-20.2],[178.9,-21.8],[179,-22.2],[179.4,-22.7],[180,-22.88]],[[-178,-17],[-178.8,-17.3],[-179.2,-17.5],[-179.6,-17.8],[-179.9,-18],[-180,-18.099999999999994]]]}] Example 3: Polygons are returned in the following format: [{"rings":[[[-7882559.1197999995,6376090.883500002],[-7893142.474300001,6042715.216800004],[-8544018.775999999,6045361.0554000065],[-8544018.775999999,6376090.883500002],[-7882559.1197999995,6376090.883500002]]]}] Example 4: Evaluated at index 2 (value is 20): 1 | ||||||||||||

$track.window(<value1>, <value2>) | Returns an array of values representing geometry and all attributes for the specified time index. The window function allows you to go forward and backward in time. - The current feature is at index 0.
- Positive values represent features that occur in the future, after the current value. For example, position 1 is the next value in the array.
- Negative numbers represent features that occurred in the past, before the previous feature. For example, -1 is the previous value in the array.
The window function is available at ArcGIS Enterprise 10.6.1. | MyField has sequentially ordered values of [10, 20, 30, 40, 50], in addition to the objectID, globalID and instant_datetime fields. The geometry the features are [{x: 1, y: 1},{x: 2, y: 2} ,{x: null, y: null},{x: 4, y: 4}, {x: 5, y: 5}] The expression is evaluated at each feature in the track. Results are returned inclusive of the start feature, and exclusive of the end feature. Example 1:$track.window(-1,0)[0] Example 2:geometry($track.window(-1,0)[0]["x"] | Example 1: When evaluated at each feature, the table shows the following results.
Example 2: Evaluated at index 2 (value is 20): 1 |