Serial chart - minimize # of categories using expressions?

[AdamCottrell]

I am trying to create a serial chart in ArcGIS Dashboard (Enterprise v12) but the unique number of categories is almost 360 and the bar chart is too overwhelming with this many values.  I would like to minimize it by using data expressions but not sure how to do it.  For example, current data is setup like:

Type	Descriptor (additional field - unrelated)
Speed Limit: 5mph	5
Speed Limit: 10mph	63
Speed Limit: 15mph	32
Speed Limit: 20mph	80
Speed Limit: 25mph	46
Warning: Dead end	3
Warning: Bicycles	10
Warning: Pedestrian	8
Regulatory: Stop	79
...and so on	etc.

I would like to group these in the chart as a single category by "Speed Limit*" so the expression would create a table like this below.  Is this possible?  If so then I could really use the help and greatly appreciate it!

Type	Descriptor	New field for Chart
Speed Limit: 5mph	5	Speed Limit
Speed Limit: 10mph	63	Speed Limit
Speed Limit: 15mph	32	Speed Limit
Speed Limit: 20mph	80	Speed Limit
Speed Limit: 25mph	46	Speed Limit
Warning: Dead end	3	Warning
Warning: Bicycles	10	Warning
Warning: Pedestrian	8	Warning
Regulatory: Stop	79	Regulatory
...and so on	etc.	etc.

[KenBuja · Accepted solution]

Here's one way to create that new field.

This takes the Schema of your original FeatureSet (line 9) and adds the additional field "Category" (line 10). It creates a dictionary for a new FeatureSet (lines 12-16), then loops through the records in the original Featureset (line 17) and copying all the attributes (lines 20-22). For the new "Category" field, it takes the value from the "Type" attribute, splits it into an array, and extracts the text before the colon (line 23). The attributes are added into a new feature (line 25) and a new FeatureSet is created from the dictionary (line 27).

var fs = FeatureSetByPortalItem(
  Portal("yourPortal"),
  "yourItem",
  0,
  ["*"],
  false
);

var theSchema = Schema(fs);
Push(theSchema.fields, { name: "Category", type: "esriFieldTypeString" });
//return theSchema;
var temp_dict = {
  fields: theSchema["fields"],
  geometryType: Schema(fs).geometryType,
  features: []
};
for (var f in fs) {
  var attrs = {};

  for (var attr in f) {
    attrs[attr] = f[attr];
  }
  attrs["Category"] = Split(f["Type"], ":")[0];

  Push(temp_dict["features"], { attributes: attrs, geometry: Geometry(f) });
}
return Featureset(temp_dict);

[AdamCottrell]

This worked almost perfectly.  I have some records that do not have the " : ".  Is there a way to change line 23  split from ":" to a number of characters?  For example, split if the first 7, or so, characters that match.  I'm not sure if the left() will work here within the split function.

[KenBuja · Accepted solution]

This would return the first seven characters

attrs["Category"] = Left(f["Type"], 7);

[AdamCottrell]

Thank you, Ken!  This was extremely helpful and saved me a lot of hours!  I truly appreciate your assistance.