Bioequivalence and Bioavailability Forum • the model matrix and the contrasts

the model matrix and the contrasts [🇷 for BE/BA]

posted by mittyri – Russia, 2024-02-22 21:21 (503 d 23:55 ago) – Posting: # 23873
Views: 3,896

Dear ElMaestro!

I (and many others) understand your degree of discontent.
Yes, this is something unexpected.
I suppose you already read this answer

I have nothing to add to this: that's a price for identifiability. The only solution I see besides you already gave is to turn off the contrasts as shown there:

f <- sample(gl(3, 4, labels = letters[1:3]))

# [1] c a a b b a c b c b a c

#Levels: a b c



g <- sample(gl(3, 4, labels = LETTERS[1:3]))

# [1] A B A B C B C A C C A B

#Levels: A B C

X0 <- model.matrix(~ f + g, contrasts.arg = list(

                   f = contr.treatment(n = 3, contrasts = FALSE),

                   g = contr.treatment(n = 3, contrasts = FALSE)))



#   (Intercept) f1 f2 f3 g1 g2 g3

#1            1  0  0  1  1  0  0

#2            1  1  0  0  0  1  0

#3            1  1  0  0  1  0  0

#4            1  0  1  0  0  1  0

#5            1  0  1  0  0  0  1

#6            1  1  0  0  0  1  0

#7            1  0  0  1  0  0  1

#8            1  0  1  0  1  0  0

#9            1  0  0  1  0  0  1

#10           1  0  1  0  0  0  1

#11           1  1  0  0  1  0  0

#12           1  0  0  1  0  1  0

—
Kind regards,
Mittyri

Complete thread:

lm and the model matrix ElMaestro 2024-02-19 09:51 [🇷 for BE/BA]
- the model matrix and the contrastsmittyri 2024-02-22 20:21
  - Yes, but.... ElMaestro 2024-02-23 17:41
    - Yes, but.... mittyri 2024-02-23 19:39
      - Yes, but.... ElMaestro 2024-02-23 22:15