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Clarify the role of pivoting in QR factorization #29976

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Nov 21, 2018
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Clarify the role of pivoting in QR factorization #29976

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Clarify the role of pivoting in QR factorization
mzaffalon Nov 9, 2018
c9577df
Update qr.jl
mzaffalon Nov 9, 2018
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4 changes: 3 additions & 1 deletion stdlib/LinearAlgebra/src/qr.jl
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Expand Up @@ -318,7 +318,9 @@ Iterating the decomposition produces the components `Q`, `R`, and if extant `p`.

The following functions are available for the `QR` objects: [`inv`](@ref), [`size`](@ref),
and [`\\`](@ref). When `A` is rectangular, `\\` will return a least squares
solution and if the solution is not unique, the one with smallest norm is returned.
solution and if the solution is not unique, the one with smallest norm is returned. When
`A` is not full rank, factorization with (column) pivoting is required to obtain a minimum
norm solution.

Multiplication with respect to either full/square or non-full/square `Q` is allowed, i.e. both `F.Q*F.R`
and `F.Q*A` are supported. A `Q` matrix can be converted into a regular matrix with
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