Labelled indices on arrays



On 05/03/2012 02:50 PM, Jaime Villate wrote:
> On 05/03/2012 12:32 PM, maxima at peutch.e4ward.com wrote:
>> I would like to create variables for each of the 2x2 possible states of
>> my model. Along the first dimension, the state is either a or b. Along
>> the second: x or y.
>>
>> I started by creating manually:
>>     variable_ax: 1;
>>     variable_ay: 33;
>>     variable_bx: 4;
>>     variable_by: 50;
>>
>> What I would like to do is something like being able to assign:
>>     variable['a]['x] : 1;
>>     variable['a]['y] : 33;
>>
>> and so on. But i get an error (assignment: cannot assign to
>> (variable['a])['x]).
> (%i2) concat('variable_,'a,'x) :: 1;
> (%o2)  1
> (%i3) concat('variable_,'a,'y) :: 33;
> (%o3)  33
> (%i4) variable_ax;
> (%o4)  1
> (%i5) variable_ay;
> (%o5)  33
I forgot to paste:

(%i6) ''(concat('variable_,'a,'x));
(%o8) 1

Jaime