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}}