topic Re: GrouBy Data Expression in ArcGIS Dashboards Questions

GrouBy Data Expression

JanelleShank — Mon, 04 Mar 2024 16:57:25 GMT

Good Afternoon, All!

I have a dataset of voting results and I can trying to create a data expression that returns the MAX value of registered voters within each district and then add the total of each MAX value to find the total number of those registered. I have written a data expression using the GoupBy function, however, it is returning a null value. I have provided examples of my data expression and data below.

var fs = FeaturesetByPortalItem(Portal("https://bedfordplanning.maps.arcgis.com"), "78eb292ce436450b85dc249bd3069741", 0, ["Precinct_name", "Reg_voters"], false)

var out_dict = {

fields: [

{name: "Precinct_Name", type: "esriFieldTypeString"},

{name: "Reg_voters", type: "esriFieldTypeString"}

features: [],

geometryType: ""

}

var maxvotes = GroupBy("out_dict", 'Precinct_Name', {name: 'Reg_voters', expression: 'Reg_Voters', statistic: "MAX"})

Thank you,

Janelle

Re: GrouBy Data Expression

KenBuja — Mon, 04 Mar 2024 17:13:06 GMT

You're using out_dict in the GroupBy, but you haven't assigned any records to it. Why aren't you using fs in the GroupBy?

Re: GrouBy Data Expression

JanelleShank — Mon, 04 Mar 2024 17:14:43 GMT

I thought by using "out_dict", I was assigning a new variable.

Re: GrouBy Data Expression

KenBuja — Mon, 04 Mar 2024 17:22:20 GMT

The first parameter of the GroupBy function is the FeatureSet that contains the data, which should be fs. The out_dict variable is just an empty FeatureSet you've created.

Re: GrouBy Data Expression

JanelleShank — Mon, 04 Mar 2024 17:27:21 GMT

Thank you, I'll give that try.

Re: GrouBy Data Expression

JanelleShank — Thu, 07 Mar 2024 16:31:24 GMT

When I replaced "out_dict" with fs, I got an error that it could not execute the expression. Do you happen to have any idea of where I am going wrong?

Re: GrouBy Data Expression

KenBuja — Mon, 04 Mar 2024 17:41:08 GMT

When using variables, don't encase them in quotes.

var maxvotes = GroupBy(fs, 'Precinct_Name', {name: 'Reg_voters', expression: 'Reg_Voters', statistic: "MAX"})

Re: GrouBy Data Expression

JanelleShank — Mon, 04 Mar 2024 17:48:00 GMT

Thank you. I removed the quotes from the variable and the expression was able to run this time. However it returned a "null" value when it should return a table, like the one below.

Do I need to return to the empty FeatureSet?

Re: GrouBy Data Expression

KenBuja — Mon, 04 Mar 2024 18:13:30 GMT

Since your data is private, I can't test it. However, I was able to test using a public service and it worked as expected, returning two items in the table with the maximum value for each aggregationMethod

var fs = FeatureSetByPortalItem( Portal("https://www.arcgis.com"), // portal item id "7b1fb95ab77f40bf8aa09c8b59045449", 0, // layer id ["*"], // fields to include false // include or exclude geometry ); GroupBy(fs, 'aggregationMethod', {name: 'TOTPOP_CY', expression: 'TOTPOP_CY', statistic: "MAX"})

Re: GrouBy Data Expression

jcarlson — Mon, 04 Mar 2024 18:24:40 GMT

GroupBy returns a FeatureSet, so return maxvotes should do it. What does your expression look like at this point?

Re: GrouBy Data Expression

JanelleShank — Thu, 07 Mar 2024 16:29:45 GMT

Thank you for your help on this! Your code helped me refine my expression and I also noticed that I had my Item number incorrect in my expression and once that was fixed I was able to apply the correct expression.

Thank you, again!

Best,

Janelle

Re: GrouBy Data Expression

JanelleShank — Thu, 07 Mar 2024 16:30:44 GMT

Thank you for your help. My expression is the same as above. Turns out it was not working correctly because I had the ID number wrong for my data.

Best,

Janelle