Re: Re: Why does Inverse[M] hesitate?

*To*: mathgroup at smc.vnet.net*Subject*: [mg54472] Re: [mg54390] Re: Why does Inverse[M] hesitate?*From*: DrBob <drbob at bigfoot.com>*Date*: Mon, 21 Feb 2005 03:44:40 -0500 (EST)*References*: <cv6t0c$6re$1@smc.vnet.net> <200502200507.AAA19929@smc.vnet.net>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

Yeah, I'd forgotten one of my pet peeves. Read Help for MatrixForm, and it says: "MatrixForm acts as a â??wrapperâ??, which affects printing, but not evaluation." But that's just not true. Bobby On Sun, 20 Feb 2005 00:07:49 -0500 (EST), David Bailey <dave at Remove_Thisdbailey.co.uk> wrote: > Skirmantas wrote: >> The Inverse function sometimes calculates the inverse of a matrix >> immediately, sometimes it does not. Try this example in Mathematica >> 5.1: >> >> A={{(1-g)-1,1},{-w P(1-g)/C,-1}}//MatrixForm >> B={{0},{-P(w+1)}}//MatrixForm >> >> I get >> Out: Inverse[(expanded A)].(expanded B) >> >> If I do just >> A={{a,b},{c,d}} >> B={{e},{f}} >> Inverse[A].B >> >> I get the final correct result. >> > If you write A= <some matrix expression> //MatrixForm it displays > beautifully, but the expression assigned to A actually contains the > MatrixForm! You can check this by looking at FullForm[A]. > > You should write A=<some matrix expression>; > A//MatrixForm > > That way the expression containing the MatrixForm gets discarded. > > BTW - This example just goes to show how useful it is to include ACTUAL > CODE with a query! > > David Bailey > dbaileyconsultancy.co.uk > > > > -- DrBob at bigfoot.com www.eclecticdreams.net

**References**:**Re: Why does Inverse[M] hesitate?***From:*David Bailey <dave@Remove_Thisdbailey.co.uk>