• Support PF! Buy your school textbooks, materials and every day products Here!

Summation Notation Ambiguity

  • Thread starter hbweb500
  • Start date
  • #1
41
1
I am working on a problem that uses the notation:

[tex]
\sum_{i,j=1}^n A_{i,j}
[/tex]

Where A is an (n x n) matrix. I am a little unsure of what the summation is over, due to the odd notation "i,j = 1". My first guess is that this is shorthand for

[tex]
\sum_{i=1}^n \sum_{j=1}^n A_{i,j}
[/tex]

But I am wondering if it could also mean the sum over the diagonal elements of the matrix, i.e.:

[tex]
\sum_{i=1}^n A_{i,i}
[/tex]

I am guessing it is the first, but I want to make absolutely sure.
 

Answers and Replies

  • #2
LCKurtz
Science Advisor
Homework Helper
Insights Author
Gold Member
9,517
733
Yes, your first guess is the standard interpretation.
 
  • #3
41
1
Thanks!
 

Related Threads for: Summation Notation Ambiguity

  • Last Post
Replies
8
Views
3K
  • Last Post
Replies
3
Views
853
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
7
Views
1K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
3
Views
685
Top