Difference: Add option to assume zero values before

janezd commented 1 year ago

Issue

Fixes #244.

It's indeed a minor change, but it may take time to merge because my boss @VesnaT excels at finding my mistakes in exactly these kinds of pull requests.

(Kidding of course. @VesnaT is meticulously great.)

Description of changes

Just to see that I understood this correctly.

With first-degree difference, values are just copied -- because zero is subtracted.
For second degree, the shift is always 1, so there are two lines to be computed. The first is again a copy, and the second is x1 = (x1 - x0) - (x0 - 0) = x1 - 2 x0.

When direction is inverted or when computing some kinds of quotients and percentages, this option is disabled.

Includes

[X] Code changes
[X] Tests
[ ] Documentation

wvdvegte commented 1 year ago

Not part of this PR, but I have noticed that selected variables are not saved when saving a workflow.

That's #243 , as I have also recently noticed.

wvdvegte commented 1 year ago

Just an idea - but why not add Difference as an option to Moving Transform, to be combined with a window size of 2 for regular difference calculation. I guess #243 won't be fixed in the next release of Timeseries, and it's a very annoying bug. Why not get rid of Difference altogether, just like Aggregate?

biolab / orange3-timeseries