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MathGroup Archive 2007

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Re: apparently I don't know how to use Map (or Apply or

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77342] Re: [mg77290] apparently I don't know how to use Map (or Apply or
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 7 Jun 2007 03:43:36 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

m = {{0.098, 0.951, 0.954}, {0.509, 0.914, 0.487}};

Table[m[[i, i]], {i, Length[m]}]

{0.098,0.914}

i = 1; #[[i++]] & /@ m

{0.098,0.914}

New in v6:

Diagonal[m]

{0.098,0.914}


Bob Hanlon

---- dbsearch04 at yahoo.com wrote: 
> I started with this:
> 
> m = {{0.098, 0.951, 0.954}, {0.509, 0.914, 0.487}}
> 
> I tried to do this
> 
> Table[#[[i, i]], {i, Length[#]}] & /@ m
> 
> It does not work, but this works
> 
> Diag := Function[x, Table[x[[i, i]], {i, Length[x]}]]; Diag[m]
> 
> !@#$%^&*(
> 
> Can anyone tell me why? I also tried: Apply, MapThread,
> DiagonalMatrix, TakeMatrix, adding () around the pure function...
> 
> I know that this is a simple problem. Would Evaluate help?
> 
> TIA.
> 
> Regards..
> 
> 



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