topic Re: Data expression to add a calculated attribute to all features? in ArcGIS Dashboards Questions

Data expression to add a calculated attribute to all features?

Jay_Gregory — Wed, 17 May 2023 16:16:50 GMT

I'm trying to easily create a data expression that adds an attribute to each feature in a data set, but I'm getting stuck on how to add an attribute to an existing feature without creating a feature from scratch, including all pre-existing attributes.

I get an execution error: "key not found - attributes.'

In short, do I have to create a brand new feature and manually reference each attribute I need, or is there an easy way to simply add an attribute to an existing feature.

var portal = Portal('https://www.arcgis.com/'); var layer = FeatureSetByPortalItem(portal, itemid) var features=[]; for (var i in layer) { var newvalue = some logic here i['attributes']['newattribute'] = newvalue Push(features,i) } return { geometryType:'', features:features }

Re: Data expression to add a calculated attribute to all features?

JohannesLindner — Wed, 17 May 2023 16:49:50 GMT

You have to create a new Featureset and copy the attributes. Luckily, you can do it in a loop, without too much manual work:

// define the new field(s) var new_fields = [ {name: "NewAttribute", type: "esriFieldTypeInteger"}, ] // create an empty featureset with existing and new fields var out_fs = { fields: Splice(Schema(layer).fields, new_fields), geometryType: Schema(layer).geometryType', features: [] } // fill the featureset for (var i in layer) { var att = {} // copy existing field values for(var field in i) { var value = i[field] att[field] = IIf(TypeOf(value) == "Date", Number(value), value) } // insert the new value(s) var new_value = 25 att["NewAttribute"] = new_value // append the feature to the featureset Push(out_fs.features, {attributes: att, geometry: Geometry(i)}) } // return return Featureset(Text(out_fs))