Skip to content

Commit 0f1e143

Browse files
committed
address reviewer comments
1 parent 54b202d commit 0f1e143

File tree

1 file changed

+8
-5
lines changed

1 file changed

+8
-5
lines changed

src/reference-manual/transforms.qmd

Lines changed: 8 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -477,10 +477,13 @@ $$
477477
For the transform, Stan uses the first part of an isometric log ratio
478478
transform; see [@egozcue+etal:2003] for the basic definitions and
479479
Chapter 3 of [@filzmoser+etal:2018] for the pivot coordinate version
480-
used here. Stan uses the isometric log ratio transform because it
481-
results in equal variances across the values of the the constrained sum to zero vector
482-
because simpler alternatives, such as setting the final element to the negative sum of the first elements; see, e.g.,
483-
[@seyboldt:2024], do not result in equal variances. The $N - 1$ unconstrained parameters are independent, however, the sum to zero constraint induces a negative correlation across the constrained values.
480+
used here. Stan uses the isometric log ratio transform because it
481+
results in equal variances of the the constrained sum to zero
482+
vector see, e.g.,[@seyboldt:2024]. Simpler alternatives, such as setting the
483+
final element to the negative sum of the first elements, do not result in
484+
equal variances. The $N - 1$ unconstrained parameters are independent, however,
485+
the sum-to-zero constraint induces a negative correlation across the
486+
constrained vector values.
484487

485488
### Zero sum transform {-}
486489

@@ -495,7 +498,7 @@ S_N = 0
495498
$$
496499
and
497500
$$
498-
y_N = -x_{N + 1} \cdot \frac{\sqrt{N \cdot (N + 1)}}{N}.
501+
y_N = -x_{N + 1} \cdot \sqrt{1 + \frac{1}{N}}.
499502
$$
500503
The for each $n$ from $N - 1$ down to $1$, let
501504
$$

0 commit comments

Comments
 (0)