Re: Function construction and also symmetric matrices
- To: mathgroup at smc.vnet.net
- Subject: [mg108540] Re: Function construction and also symmetric matrices
- From: Ray Koopman <koopman at sfu.ca>
- Date: Mon, 22 Mar 2010 02:40:54 -0500 (EST)
- References: <hnva64$88k$1@smc.vnet.net> <hnvo3m$egu$1@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}}