Calculated difference

[jamesrkg]

@jjdelc are you able to add support for Calculated differences?

https://crunch.io/dev/features/subtotal-differences/

[jjdelc]

Yeah, I see there's a .add_subtotal I will read through that and see how it would be best to add the subtotal differences there

[jjdelc]

How does this look:

var.add_subtotal("F - M", {
            "add": ["Female"],
            "minus": ["Male"]
        }, anchor="bottom")

It is overloading the Variable.add_subtotal method to detect if the 2nd argument (the categories) is a dictionary, we will use those values as positive and negative.

Another alternative is to have a separate function for when you want the subtotal to include substractions, like:

var.add_subtotal_differences("F - M", ["Female"], ["Male"], anchor="bottom")

[jamesrkg]

A new method would be cleaner, I believe. Following from your example I imagine usage such as:

var = var.add_subtotal(name="Promoters", categories=[9, 10], anchor="bottom")
var = var.add_subtotal(name="Detractors", categories=[1, 2, 3, 4, 5, 6], anchor="bottom")
var = var.add_subtotal_difference(name="NPS", add=["Promoters"], subtract=["Detractors"], anchor="bottom")

Any reason why the add/subtract args should be lists? Can we simplify to str or is this future-proofing a use case I'm not aware of?

[jamesrkg]

@jjdelc is it possible to add a difference calculation without creating/showing its dependent subtotals? For example would it be possible to add an NPS without adding Promoter and Detractor subtotals?

Perhaps I misunderstood your original example and "Female"/"Male" were category names rather than subtotal names?

If so, would this kind of usage be viable?

var = var.add_subtotal_difference(name="NPS", add=[9, 10], subtract=[1, 2, 3, 4, 5, 6], anchor="bottom")

[jjdelc]

Yes, the subtotal does not need to show the previous ones. but you have to indicate the items:

var = var.add_subtotal_difference(name="NPS", add=[9, 10], subtract=[1, 2, 3, 4, 5, 6], anchor="bottom")

In my example, I was abusing the fact that you can indicate either category IDs or category names.

[jamesrkg]

Ok great - this is preferable to my original assumption about naming subtotals anyway.