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Re: Can't use subscripted variables in function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124218] Re: Can't use subscripted variables in function
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Sat, 14 Jan 2012 02:53:48 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <je96qv$j85$1@smc.vnet.net> <jebngu$1bb$1@smc.vnet.net>
  • Reply-to: drmajorbob at yahoo.com

a[i] is less cluttered than Subscript[a,i], it works better as a variable,  
and it's easier to enter and access.

If you want a[i] to LOOK like Subscript[a,i] in displayed results, you can  
execute:

subFunction[
   a_Symbol] := (MakeExpression[SubscriptBox[ToString@a, i_], f_] :=
    MakeExpression[RowBox[{ToString@a, "[", i, "]"}]];
   MakeBoxes[a[i_], f_] :=
    SubscriptBox[MakeBoxes[a, f], MakeBoxes[i, f]])

subFunction[a]
Array[a, 10]

{Subscript[a, 1], Subscript[a, 2], Subscript[a, 3], Subscript[a, 4], \
Subscript[a, 5], Subscript[a, 6], Subscript[a, 7], Subscript[a, 8], \
Subscript[a, 9], Subscript[a, 10]}

You'll see subscripts only when a value is not defined, but that's true  
for subscripted variables, too. For instance:

a[2] = 3;
Subscript[a, 5] = 12;
Array[a, 10]

{Subscript[a, 1], 3, Subscript[a, 3], Subscript[a, 4], 12, \
Subscript[a, 6], Subscript[a, 7], Subscript[a, 8], Subscript[a, 9], \
Subscript[a, 10]}

and also

Table[Subscript[a, n], {n, 10}]

{Subscript[a, 1], 3, Subscript[a, 3], Subscript[a, 4], 12, \
Subscript[a, 6], Subscript[a, 7], Subscript[a, 8], Subscript[a, 9], \
Subscript[a, 10]}

Bobby

On Fri, 13 Jan 2012 03:52:54 -0600, Chris Young <cy56 at comcast.net> wrote:

> On 2012-01-10 10:56:36 +0000, Ralph Dratman said:
>
>> Is this just a discussion about how things look on the screen -- or is
>> there some deeper difference between Mathematica's "array" indices and
>> properly-implemented subscripts?
>
> I was looking for subscripted variables to conveniently extend notation
> for things such as points determining a polynomial, and so on. Formulas
> to do this kind of thing appear in all the math refererences with
> subscripted variables, and I think it's the most natural notation.
> We're not really interested in an array of points, just the individual
> points, in this case. It's simply a more uncluttered notation.
>
> Chris
>
>


-- 
DrMajorBob at yahoo.com



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