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MathGroup Archive 2006

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Re: Convert from String to variable

  • To: mathgroup at smc.vnet.net
  • Subject: [mg70241] Re: [mg70229] Convert from String to variable
  • From: Bruce Colletti <vze269bv at verizon.net>
  • Date: Mon, 9 Oct 2006 01:55:55 -0400 (EDT)

Peng

Try this for array variables x[y,z,...].  Mathematica 5.2.

Bruce

------------

xconvert@X_List := Map[ToExpression@
    StringJoin[ToString@Head@#, Sequence[ToString /@ (List @@ #)]] &, X];

(* Example #1 *)

X = Flatten@Array[a, {3, 3, 3}, {0, 0, 0}];
MapThread[#1 -> #2 &, {X, xconvert@X}]

(* Example #2 *)

X = {z[4, 5, 6, 7], y[0]};
MapThread[#1 -> #2 &, {X, xconvert@X}]

Out[50]=
{a[0, 0, 0] -> a000, a[0, 0, 1] -> a001,
   a[0, 0, 2] -> a002, a[0, 1, 0] -> a010,
   a[0, 1, 1] -> a011, a[0, 1, 2] -> a012,
   a[0, 2, 0] -> a020, a[0, 2, 1] -> a021,
   a[0, 2, 2] -> a022, a[1, 0, 0] -> a100,
   a[1, 0, 1] -> a101, a[1, 0, 2] -> a102,
   a[1, 1, 0] -> a110, a[1, 1, 1] -> a111,
   a[1, 1, 2] -> a112, a[1, 2, 0] -> a120,
   a[1, 2, 1] -> a121, a[1, 2, 2] -> a122,
   a[2, 0, 0] -> a200, a[2, 0, 1] -> a201,
   a[2, 0, 2] -> a202, a[2, 1, 0] -> a210,
   a[2, 1, 1] -> a211, a[2, 1, 2] -> a212,
   a[2, 2, 0] -> a220, a[2, 2, 1] -> a221, a[2, 2, 2] -> a222}

Out[52]=
{z[4, 5, 6, 7] -> z4567, y[0] -> y0}

=====================
From: "PengYu.UT at gmail.com" <PengYu.UT at gmail.com>
To: mathgroup at smc.vnet.net
Subject: [mg70241] [mg70229] Convert from String to variable

I want generate some code like below.

{a[0][0][0] -> a000, a[0][0][1] -> a001,
   a[0][0][2] -> a002, a[0][1][0] -> a010,
   a[0][1][1] -> a011, a[0][1][2] -> a012,
   a[0][2][0] -> a020, a[0][2][1] -> a021,
   a[0][2][2] -> a022, a[1][0][0] -> a100,
   a[1][0][1] -> a101, a[1][0][2] -> a102,
   a[1][1][0] -> a110, a[1][1][1] -> a111,
   a[1][1][2] -> a112, a[1][2][0] -> a120,
   a[1][2][1] -> a121, a[1][2][2] -> a122,
   a[2][0][0] -> a200, a[2][0][1] -> a201,
   a[2][0][2] -> a202, a[2][1][0] -> a210,
   a[2][1][1] -> a211, a[2][1][2] -> a212,
   a[2][2][0] -> a220, a[2][2][1] -> a221, a[2][2][2] -> a222}

I'm looking for an automated way to generate the assignments for
a[i][j][k] (i = 1...n,j=1...n,k=1...n).

One way that I think of is
Flatten[ Table[a[i][j][k] -> "a" <> ToString[i] <> ToString[j] <>
ToString[k], {i, 0, 2}, {j, 0, 2}, {k, 0, 2}]].

But this method requires to convert the strings to variables. Is it
possible to do this in Mathematica?

Are there any better solution to generate the assignment list?

Thanks,
Peng


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