Arcade data expression resulting in Nan when summed

Question

I am trying to return the sum of integer fields in a layer, however, am getting a NaN result. I have tried with Count and the correct number appears, so why does Sum not work? What am I missing here?

I am using this in a data expression to use in Dashboards list widget. Any pointers are greatly appreciated!!

var features = FeatureSetByPortalItem(
  Portal('https://adcgis.maps.arcgis.com'),
  '91feaa24f7d34f9299f5b99cbd7328ed',
  1,
  ["C18_Indst_URAdr_AgriForestFish"],
  false
);
Sum(features);

Result	Value
Result	NaN
Type	Number

jcarlson · Answer

Oh, I'm sorry! I thought this was an Advanced Formatting thing, I missed the part about it being a Data Expression. A Data Expression needs a FeatureSet as its output.

You could write this up as a Data Expression easily enough, but can I ask how you're using the data in your dashboard? If all you need is the number, you could get that into something like an Indicator widget without needing a separate expression.

In any case, the easiest way to get an output FeatureSet is to use GroupBy, which can handle the aggregation for you, too.

var features = FeatureSetByPortalItem(
  Portal('https://adcgis.maps.arcgis.com'),
  '91feaa24f7d34f9299f5b99cbd7328ed',
  1,
  ["C18_Indst_URAdr_AgriForestFish"],
  false
);

return GroupBy(
    features,
    {name: 'id', expression: '1'},
    {name: 'the_sum', expression: 'C18_Indst_URAdr_AgriForestFish', statistic: 'SUM'}
)

Hayley · Answer

Hi @jcarlson, thanks for explaining!

The expression now results in the correct number:

var features = FeatureSetByPortalItem(
  Portal('https://adcgis.maps.arcgis.com'),
  '91feaa24f7d34f9299f5b99cbd7328ed',
  1,
  ["C18_Indst_URAdr_AgriForestFish"],
  false
);
return(Sum(features, 'C18_Indst_URAdr_AgriForestFish'))

However in dashboards it says the Arcade expression is unable to be executed? How do I enable it to be used in my widgets?

jcarlson · Answer

When you use the Sum function with a single parameter, it expects an array of summable values.

When you're using a FeatureSet, you need to supply a second parameter with the field name you want summed, as there could be any number of fields in a FeatureSet. Even when you only specify a single field, it will likely still have an ObjectID field, so it needs to be told which field you want.

Try Sum(features, 'C18_Indst_URAdr_AgriForestFish')