| Author |
Comment/Response |
Alexander
|
 08/18/05 04:27am
Hello!
Here is simple example of defining list:
b = Table[Symbol["a" <> ToString[i] <> ToString[j]], {i, 2}, {j, 2}];
a11 = IdentityMatrix[2];
b[[1,1]][[1,1]]
Output will be number 1.
Then we type another command:
b[[1,1]][[1,1]]=2
wich cause error message.
If we type ?b the structure of b can be seen:
Global`b
b = {{a11, a12}, {a21, a22}}
And I wonder, how to change elements of aij from b? It's interesing question about how mathematica think things and how evaluate them.
So, the questions are:
1) Why code above produce error message?
2) What difference between b[[1,1]][[1,1]] and
b[[1,1,1,1]] notation?
Here is an example concerning the second question:
This code doesn't produce error:
a11 = IdentityMatrix[2];
b = Table[Symbol["a" <> ToString[
i] <> ToString[j]], {i, 2}, {j, 2}];
b[[1, 1, 1, 1]] = 3
but this does:
a11 = IdentityMatrix[2];
b = Table[Symbol["a" <> ToString[
i] <> ToString[j]], {i, 2}, {j, 2}];
b[[1, 1]][[1, 1]] = 3
Why?
Sorry for my obscure speech, and thanks for your answers!
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