Re: Function construction and also symmetric matrices
- To: mathgroup at smc.vnet.net
- Subject: [mg108568] Re: Function construction and also symmetric matrices
- From: "Diamond, Mark" <dot at dot.dot>
- Date: Wed, 24 Mar 2010 04:40:00 -0500 (EST)
- References: <hnva64$88k$1@smc.vnet.net> <hnvo3m$egu$1@smc.vnet.net> <ho76uf$sm$1@smc.vnet.net>
Brilliant. Thank you, both Raffy and Ray. "Ray Koopman" <koopman at sfu.ca> wrote in message news:ho76uf$sm$1 at smc.vnet.net... > On Mar 20, 12:46 am, "Diamond, Mark" <d... at dot.dot> wrote: >> Thank you Ray. >> >> Have you any thoughts about the second question? >> >> Cheers, >> Mark > > In[1]:= > makesymat[n_] := ToExpression["symat[" <> ToString@n <> "] := > Function[" <> ToString@Table[ > Which[i > j, SequenceForm["#[[",(i-1)(i-2)/2 + j,"]]"], > i < j, SequenceForm["#[[",(j-1)(j-2)/2 + i,"]]"], > True, "1"], {i,n},{j,n}] <> "]" ] > > In[2]:= makesymat[4] > > In[3]:= ?symat > > Global`symat > > symat[4] := {{1, #1[[1]], #1[[2]], #1[[4]]}, > {#1[[1]], 1, #1[[3]], #1[[5]]}, > {#1[[2]], #1[[3]], 1, #1[[6]]}, > {#1[[4]], #1[[5]], #1[[6]], 1}} & > > In[4]:= symat[4]@{a,b,c,d,e,f} > > Out[4]= {{1, a, b, d}, > {a, 1, c, e}, > {b, c, 1, f}, > {d, e, f, 1}} >