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February 10th, 2019, 08:47 AM  #1 
Newbie Joined: Feb 2019 From: Poland Posts: 2 Thanks: 0  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 
February 10th, 2019, 11:10 AM  #2 
Senior Member Joined: Sep 2016 From: USA Posts: 559 Thanks: 324 Math Focus: Dynamical systems, analytic function theory, numerics 
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 11:20 AM. 
February 10th, 2019, 12:16 PM  #3 
Newbie Joined: Feb 2019 From: Poland Posts: 2 Thanks: 0 
Thank you very much!!, you have answered my question 

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matematical, mathematical, matrix, notacion, notation 
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