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clarify pinv documentation #29793

Merged
merged 2 commits into from
Oct 25, 2018
Merged

clarify pinv documentation #29793

merged 2 commits into from
Oct 25, 2018

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stevengj
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@stevengj stevengj commented Oct 24, 2018

The pinv documentation falsely implied that it discarded singular values σ ≤ tol, when in fact it discards σ ≤ tol max(σ). This PR corrects the docstring.

(σ ≤ tol max(σ) is a good criterion! tol should be a dimensionless quantity that doesn't depend on the overall scaling/units of the matrix. I was relieved when I checked the source code and verified that tol was dimensionless.)

The `pinv` documentation falsely implied that it discarded singular values `σ > tol`, when in fact it discards `σ > tol max(σ)`.  This PR corrects the docstring.

(`σ > tol max(σ)` is a good behavior!  `tol` should be a dimensionless quantity that doesn't depend on the overall scaling/units of the matrix.)
@stevengj stevengj added docs This change adds or pertains to documentation linear algebra Linear algebra labels Oct 24, 2018
@stevengj stevengj requested a review from andreasnoack October 24, 2018 14:16
@simonbyrne
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simonbyrne commented Oct 24, 2018

Let's also rename it to rtol to emphasise this: since it's currently a positional argument, it won't be breaking, but it would make it clearer.

Though probably not in this PR, we may want to make it a keyword arg (to keep it consistent with isapprox).

@stevengj stevengj merged commit 2996521 into master Oct 25, 2018
@stevengj stevengj deleted the stevengj-patch-3 branch October 25, 2018 12:28
KristofferC pushed a commit that referenced this pull request Oct 29, 2018
* clarify pinv documentation

The `pinv` documentation falsely implied that it discarded singular values `σ > tol`, when in fact it discards `σ > tol max(σ)`.  This PR corrects the docstring.

(`σ > tol max(σ)` is a good behavior!  `tol` should be a dimensionless quantity that doesn't depend on the overall scaling/units of the matrix.)

* rename tol -> rtol

(cherry picked from commit 2996521)
KristofferC pushed a commit that referenced this pull request Feb 11, 2019
* clarify pinv documentation

The `pinv` documentation falsely implied that it discarded singular values `σ > tol`, when in fact it discards `σ > tol max(σ)`.  This PR corrects the docstring.

(`σ > tol max(σ)` is a good behavior!  `tol` should be a dimensionless quantity that doesn't depend on the overall scaling/units of the matrix.)

* rename tol -> rtol

(cherry picked from commit 2996521)
KristofferC pushed a commit that referenced this pull request Feb 20, 2020
* clarify pinv documentation

The `pinv` documentation falsely implied that it discarded singular values `σ > tol`, when in fact it discards `σ > tol max(σ)`.  This PR corrects the docstring.

(`σ > tol max(σ)` is a good behavior!  `tol` should be a dimensionless quantity that doesn't depend on the overall scaling/units of the matrix.)

* rename tol -> rtol

(cherry picked from commit 2996521)
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5 participants