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From: Peter Breitfeld on 25 Jul 2010 02:00
miguelwon wrote:

> Hello.
>
> I'm working with some expressions that are dependent of several
> variables co1, co2, ... , con. I would like to know how can I assign
> values iteratively to some of these variables. I tried:
>
> For[i=1,i<=100,i++,
> Symbol["co"<>ToString[i]]=0;
> ];
>
> but it doesn't work. For each iteration it says coi is Protected.
> Can someone help me?
>
> Thanks
>

The error occurs, because you tried to assign the value 0 to an
Expression with Head Symbol. One way to make lists of symbols is to use
Array like this:

Array[co,5] gives
{co[1], co[2], co[3], co[4], co[5]}

If you like to name your variables co1, co2,... (bad idea) you could do the
following

CC=Array["cc"<>ToString[#]&,5]
{"cc1", "cc2", "cc3", "cc4", "cc5"}

These are not Symbols but Strings, which is bad.

So I would not recommend this, because you can't easily assign values to
the list, whereas in the first case it's easy:

Do[co[i]=10+i,{i,10}]

co/@Range[5]
{11, 12, 13, 14, 15}

--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de

From: Leonid Shifrin on 25 Jul 2010 02:01
This will work, regardless of whether the variables already had some values
or not:

Table[ToExpression["co" <> ToString[i], InputForm,
Function[s, s = 0, HoldAll]], {i, 100}]

I would recommend using indexed variables like co[1], co[2] etc
instead of co1, co2, etc - then it is even much easier:

In[10]:= Clear[co];
In[11]:= Do[co[i] = 0, {i, 100}]

In[12]:= co /@ Range[10]

Out[12]= {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}

Indexed variables are generally easier to manipulate than Symbols,
particularly when
you have many of them and want to manipulate them programmatically.

Regards,
Leonid


On Sat, Jul 24, 2010 at 1:07 PM, miguelwon <miguelwon(a)gmail.com> wrote:

> Hello.
>
> I'm working with some expressions that are dependent of several
> variables co1, co2, ... , con. I would like to know how can I assign
> values iteratively to some of these variables. I tried:
>
> For[i=1,i<=100,i++,
> Symbol["co"<>ToString[i]]=0;
> ];
>
> but it doesn't work. For each iteration it says coi is Protected.
> Can someone help me?
>
> Thanks
>
>


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