Extract sub matrices

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Abhijit Das
Abhijit Das 2012-3-15
I have a matrix A=magic(4); (say)
I want 4x4 matrices from A such that the 16 matrices can be saved with different names.
a1=(16 2;5 11)
a2=(16 2 3; 5 11 10)
a3=( 2 3 13; 11 10 8)
a4=(3 13; 3 13)
a5=(16 2; 5 11; 9 7)
a6=(16 2 3; 5 11 10; 9 7 6 )
a7=(2 3 13; 11 10 8; 7 6 12)
a8=(3 13; 10 8;6 12)
a9=(5 11; 9 7;4 14)
a10= (5 11 10 ; 9 7 6; 4 14 15)
a11=(11 10 8; 7 6 12; 14 15 1)
a12=(10 8; 6 12; 15 1)
a13=(9 7; 4 14 )
a14=(9 7 6; 4 14 15)
a15=(7 6 12; 14 15 1)
a16=( 6 12; 15 1)
I want to use loop so that I can extract matrices from other large matrices.

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回答（2 个）

Image Analyst
Image Analyst 2012-3-15
That's okay to hard code for a small matrix, like you did (almost), but not advisable for a large matrix. See the FAQ http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F
Jan
Jan 2012-3-15
I use A1, A2, ... for arrays up to 3 elements only. Otherwise using a cell A{1}, A{2}, ... is much more convenient, efficient and easier to debug. Reading the FAQ is recommended. At least the best-of, because it is asked with such a high frequency, that it gets a waste of time:
  1. FAQ 4.6: Create A1, A2, ... in a loop
  2. FAQ 6.1: 0.3 - 0.2 - 0.1 ~= 0
  3. FAQ 4.16: Avoid eval
  4. FAQ 5.16: Share data between callbacks
This should not encourage you not to read the other sections also.

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