Re: Did something change?

*To*: mathgroup at smc.vnet.net*Subject*: [mg58130] Re: Did something change?*From*: "Stefan Linnik" <sjl.news56 at tiscali.co.uk>*Date*: Sun, 19 Jun 2005 03:43:40 -0400 (EDT)*References*: <d90tjl$9bc$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

To do direct assignments using = the list must first be initialised. Also f[i] should be f[[i]] Also as well f[[i, 1, 3]]= 7 works better than f[[i]][[1,3]]= 7 f=Array[0&,{10,8,8}]; Do[ f[[i]]=IdentityMatrix[8]; f[[i,1,3]]=7, {i,10} ] Stefan Linnik ~~~~~~~~ "Ronald Bruck" <bruck at math.usc.edu> wrote in message news:d90tjl$9bc$1 at smc.vnet.net... > Recently I created a list of several matrices, something like > > Do[F[i] = IdentityMatrix[8]; F[i][[1,3]] = 7, {i,10}] > > and was surprised to get the message that F[i] wasn't a symbol. I'm > pretty sure code similar to that worked prior to Mathematica 5. Did > something change? > > I've also tried Symbolize[F[i]] in that loop, but it doesn't help; > Mathematica refuses to access part [[1,3]] of F[i], claiming F[i] isn't > a symbol. > > How are you supposed to set the individual values of a matrix if you > can't do this? This is an EXTREMELY unhelpful "feature". > > --Ron Bruck >