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Re: Do I have to worry about "Left" division for matrices?

• To: mathgroup at smc.vnet.net
• Subject: [mg94253] Re: Do I have to worry about "Left" division for matrices?
• From: hayes.tyler at gmail.com
• Date: Tue, 9 Dec 2008 06:57:33 -0500 (EST)
• References: <200812041217.HAA27795@smc.vnet.net> <ghdmo8$fjj$1@smc.vnet.net>

Thanks for all of the help and clarification. I like Daniel's
solutionn best as it seems (to me at least) to be the most transparent
method. Nonetheless, I may do a quick Timing[] test on Inverse[A].b
versus LinearSolve[A,b] to see which performs best.

Cheers,

t.




On Dec 6, 6:13 am, Daniel Lichtblau <d... at wolfram.com> wrote:
> Tyler wrote:
> > Hello All:
>
> > I am currently in the process of rewriting some old code into
> > Mathematica. One of the things I've come across is the matrix
> > operation
>
> > A \ b
>
> > Which is defined as "left division." In other words (if I have this
> > right):
>
> > A \ b = inv(A)*b
>
> > and "right division" is
>
> > b / A = b*inv(A)
>
> > I guess my question is, does mathematica make the distinction between
> > left and right division, or is this more or less related to the
> > algorithm used by the solver (I am using numerical values by the way,
> > and not a symbolic solution)?
>
> > Cheers,
>
> > t.
>
> The (preferred) Mathematica equivalents would be LinearSolve[A,b] and
> LinearSolve[Transpose[A],b] respectively.
>
> Mathematica does not support an infix form of this sort of division, so
> the immediate question is moot.
>
> Daniel Lichtblau
> Wolfram Research

• References:
  • Do I have to worry about "Left" division for matrices?
    • From: Tyler <hayes.tyler@gmail.com>