Use a data expression to create a new field based on values in another field for use in a pie chart

[Bec]

Hi!  I'm trying to build a data expression in an ArcGIS Online dashboard that will take a field called, HOUR_OF_CRASH, which is an integer field and not a time field, and populate a new field called, TOD, which will be a text field for the time of day the hour falls within so that the new field can be used to build a pie chart within the dashboard.  The current data expression is shown below.

var portal = Portal("https://www.arcgis.com");

var fs = FeatureSetByPortalItem('d651aa4112e5408ea9a1cfabecd6485c', 23)
// Create schema for the returned FeatureSet
var fields = [
    { name: "HOUR_OF_CRASH", type: "esriFieldTypeInteger" },
    { name: "TOD", type: "esriFieldTypeString" }
];

var features = [];

for (var f in fs) {
    var hour = f.HOUR_OF_CRASH;
    var tod;

    if (hour >= 0 && hour <= 5){
        tod = "Night";
    } else if (hour >= 6 && hour <= 8){
        tod = "Morning";
    } else if (hour >= 9 && hour <= 15){
        tod = "Day";
    } else if (hour >= 16 && hour <= 23){
        tod = "Evening";
    } else {
        tod = null;
    }

    Push(features, {
        attributes: {
            HOUR_OF_CRASH: hour,
            TOD: tod
        }
    });
}

Unfortunately, this data expression won't function within the dashboard and doesn't give me quite the output I am looking for in the end.  See the below image of the output.

 My experience with data expression is relatively limited.  Any advice would be greatly appreciated!

Bec

[RPGIS · Accepted solution]

Hi @Bec,

So the issue is that you are not returning a feature. When creating a custom data expression you should return a value similar to the one below.

var portal = Portal("https://www.arcgis.com");

var fs = FeatureSetByPortalItem('d651aa4112e5408ea9a1cfabecd6485c', 23)
// Create schema for the returned FeatureSet
var fields = [
    { name: "HOUR_OF_CRASH", type: "esriFieldTypeInteger" },
    { name: "TOD", type: "esriFieldTypeString" }
];

var features = []; 
for (var f in fs) {
    var hour = f.HOUR_OF_CRASH;
    var tod = When( hour >= 0 && hour <= 5, "Night", hour >= 6 && hour <= 8, "Morning", hour >= 9 && hour <= 15, "Day", 16 && hour <= 23, "Evening", Null )
	Push( features, { attributes: { HOUR_OF_CRASH: hour, TOD: tod } })
	}
return FeatureSet( fields, Values, geometry:'' )

[KenBuja]

Also note that you can make the When statement more concise

var tod = When(hour >= 0 && hour <= 5, "Night",
               hour <= 8, "Morning",
               hour <= 15, "Day",
               hour <= 23, "Evening",
               Null
);

[Bec]

Also, very good input from you as well Ken!  Thank you for sharing your knowledge and experience.

[Bec]

Yes, RPGIS, your input about returning a FeatureSet was valuable in helping me get to my final output.  I made a few more adjustments to the final data expression and what you see below is the working version along with an image of the output.

/// Connect to portal layer
var portal = Portal("https://www.arcgis.com");
var fs = FeatureSetByPortalItem(
    portal,
    "d651aa4112e5408ea9a1cfabecd6485c",
    23
);
// Portal layer is a proxy to REST Service layer called CoC Crash Data
// If REST Service layer attributes change may affect data expression

// --- Define Output Schema ---
var fields = [
    { name: "HOUR_OF_CRASH", type: "esriFieldTypeInteger" },
    { name: "TOD", type: "esriFieldTypeString" },
    { name: "SEVERITY_BY_TYPE_CD", type: "esriFieldTypeString" },
    { name: "CRASH_TYPE_CD", type: "esriFieldTypeString" },
    { name: "DAY_IN_WEEK_CD", type: "esriFieldTypeString" },
    { name: "Month", type: "esriFieldTypeDouble" },
    { name: "HIN", type: "esriFieldTypeSmallInteger" },
    { name: "ODPS_SPEED_IND", type: "esriFieldTypeString" },
    { name: "FUNCTIONAL_CLASS_CD", type: "esriFieldTypeString" },
    { name: "ODOT_LANES_NBR", type: "esriFieldTypeDouble" },
    { name: "ODOT_YOUNG_DRIVER_IND", type: "esriFieldTypeString" },
    { name: "ODPS_SENIOR_DRIVER_IND", type: "esriFieldTypeString" },
    { name: "DISTRACTED_DRIVER_IND", type: "esriFieldTypeString" },
    { name: "WEATHER_COND_CD", type: "esriFieldTypeString" },
    { name: "LIGHT_COND_PRIMARY_CD", type: "esriFieldTypeString" },
    { name: "ROAD_COND_PRIMARY_CD", type: "esriFieldTypeString" },
    { name: "ODOT_CRASH_LOCATION_CD", type: "esriFieldTypeString" }
];

var features = [];

// --- Build Output Records ---
for (var f in fs) {

    var hour = f.HOUR_OF_CRASH;

    var tod = When(
        hour >= 0 && hour <= 5, "Night",
        hour >= 6 && hour <= 8, "Morning",
        hour >= 9 && hour <= 15, "Day",
        hour >= 16 && hour <= 23, "Evening",
        null
    );

    Push(features, {
        attributes: {
            HOUR_OF_CRASH: hour,
            TOD: tod,
            SEVERITY_BY_TYPE_CD: f.SEVERITY_BY_TYPE_CD,
            CRASH_TYPE_CD: f.CRASH_TYPE_CD,
            DAY_IN_WEEK_CD: f.DAY_IN_WEEK_CD,
            Month: f.Month,
            HIN: f.HIN,
            ODPS_SPEED_IND: f.ODPS_SPEED_IND,
            FUNCTIONAL_CLASS_CD: f.FUNCTIONAL_CLASS_CD,
            ODOT_LANES_NBR: f.ODOT_LANES_NBR,
            ODOT_YOUNG_DRIVER_IND: f.ODOT_YOUNG_DRIVER_IND,
            ODPS_SENIOR_DRIVER_IND: f.ODPS_SENIOR_DRIVER_IND,
            DISTRACTED_DRIVER_IND: f.DISTRACTED_DRIVER_IND,
            WEATHER_COND_CD: f.WEATHER_COND_CD,
            LIGHT_COND_PRIMARY_CD: f.LIGHT_COND_PRIMARY_CD,
            ROAD_COND_PRIMARY_CD: f.ROAD_COND_PRIMARY_CD,
            ODOT_CRASH_LOCATION_CD: f.ODOT_CRASH_LOCATION_CD
        }
    });
}

// --- Return FeatureSet (non-spatial) ---
return FeatureSet({
    fields: fields,
    features: features
});

 

[RPGIS]

You could go a more programmatic route.

var fs = FeatureSetByPortalItem('d651aa4112e5408ea9a1cfabecd6485c', 23)
// Create schema for the returned FeatureSet
var HRC = "HOUR_OF_CRASH" ; var TODn = "TOD"
var FDict = Dictionary( HRC, "esriFieldTypeInteger", TODn, "esriFieldTypeString" )
var fields = [
    { name: HRC, type: FDict[HRC] },
    { name: TODn, type: FDict[TODn] }
];

var features = [];
for (var f in fs) {
    FDict[HRC] = f.[HRC]
    FDict[TODn] = When( hour >= 0 && hour <= 5, "Night", hour <= 8, "Morning", hour <= 15, "Day", hour <= 23, "Evening", Null )
 	Push( features, { attributes: FDict })
 	}
return FeatureSet( fields:fields, features:features, geometry:'' )