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February 10th, 2019, 07:47 AM   #1
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Mathematical notation of matrix

Hi,
I would like to know how is the mathematical notation to describe the selection of a part of a Matrix, eg. in Matlab B=A(1:3,1:2)

I appreciate your help
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February 10th, 2019, 10:10 AM   #2
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What you want is usually called a submatrix of $A$, but I don't know of any standard notation. There are a few ways I can think of that are reasonable to write this.

1. $B$ is the $3 \times 2$ submatrix of $A$ obtained by truncation to its first 3 rows and first 2 columns.

2. $B$ is the $3 \times 2$ submatrix of $A$ with entries given by $(a_{ij})$ for $1 \leq i \leq 3$ and $1 \leq j \leq 2$.

I think if you specify the exactly size of $B$ it's not hard for readers to understand. If you are writing a paper which needs to describe a lot of these "slicing" operations, it is best to decide on a reasonable notation and define it ahead of time.

Last edited by skipjack; February 10th, 2019 at 10:20 AM.
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February 10th, 2019, 11:16 AM   #3
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Thank you very much!!, you have answered my question
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