Yes, but.... [🇷 for BE/BA]

posted by ElMaestro  – Denmark, 2024-02-23 23:15 (56 d 12:14 ago) – Posting: # 23880
Views: 644

(edited by on 2024-02-24 00:00)

Hi Mittyri,

❝ may be I misunderstood your


❝ ❝ is not full rank. Neither is does it contain a column for every level of every factor.

❝ The solution you proposed with qr() does not give a column for every level of every factor

> (MakeFullRank(model.matrix(~ f + g)))

❝    Q       

❝ 1  1 0 0 1 0

❝ 2  1 0 1 1 0

❝ 3  1 1 0 0 1

❝ 4  1 0 1 1 0

❝ 5  1 0 0 0 0

❝ 6  1 0 0 0 1

❝ 7  1 0 1 0 0

❝ 8  1 1 0 0 0

❝ 9  1 0 1 1 0

❝ 10 1 1 0 0 0

❝ 11 1 0 0 0 1

❝ 12 1 1 0 0 1


A full rank model matrix means there are not more columns than the rank. Then XtX becomes invertible.
A model matrix with a column for every level of every factor (plus intercept) is not the same. Rather that's redundancy. XtX now becomes trouble :-)
My function creates a full rank model matrix.

Pass or fail!
ElMaestro

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