[Work in progress] BarnettZehnwirth formula helper (with some refactor)#642

Merged

henrydingliu merged 4 commits intocasact:BZ_w_dropfrom

danielfong-act:BZ_w_drop

Jan 7, 2026

Commits on Jan 6, 2026

Initial PTF_formula commit.
danielfong-act
committed
origin trend groups (alpha) are passed as tuples denoting ranges to PTF_formula. Removes first year's origin trend group, if specified (intercept term takes its place).
danielfong-act
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Rmoved mostly useless multicollinearity warning. Users should exercise caution in genral
danielfong-act
committed

Commits on Jan 7, 2026

makes development/tests/test_barnzehn use PTF_formula to construct the formula for test_bz_2008. Tweaks alpha parameters to be additive again.
danielfong-act
committed