Sum/aggregate expression on a array of json data property?

I have a table in perspective that’s data property is a array of json objects. We do this so we’re able to manipulate row background colors.

In this same table, I want to get a sum of a column, in this case, a boolean column named “Yes” with a check box to count how many were checked. I am using sum({}, "Yes") but this is not calculating the correct value.

Do these aggregate functions only work on actual dataset type data properties? Is there a way around this or will I have to resort to some scripting on a table extension function?

According to the user manual, sum only accepts datasets, or an arbitrary amount of ints/floats as parameters to sum up, and not json data.

The script to solve your problem should be very simple, perhaps a custom property on your table with a binding onto–something like this:

# given this is in, say, a property binding on a 
# custom property which references your table's
sum = 0
for row in value: # 'value' is your table's
    if row["Yes"] == True:
        sum += 1
return sum
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At some point in the future, we’re planning to have the aggregate expression functions work on json objects and arrays, but it’s a non-trivial amount of refactoring to make sure it doesn’t break other things.


Good to know. I tried doing a sum(toDataSet({}),"Yes") as an expression, but realized the toDataSet just turned it into a dataset with a single column of qualified values.