fundamental principle of multiplication

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a 2013-10-11

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评论： a 2013-10-14

采纳的回答： Jos (10584)

i have 4 numbers as a row vector, p=[ 1 -1 j -j ];

Now, total number of different 4 digit numbers formed using elements of "p" is 4^4=256

Thus i need a 256*4 matrix.

How to create such a 256*4 matrix ?

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Image Analyst 2013-10-12

What is a 4 digit number? Can you give an example of the first 6 rows of what you want at the result?

a 2013-10-12

编辑：a 2013-10-12

data.txt

@Image Analyst:

Here a 4 digit number is like,

1 1 1 1 ; 1 1 1 -1 ; 1 1 1 i ; 1 1 1 -i ; 1 1 -1 1; ... and so on(till 256 row vectors hence a 256x4 matrix).

first 6 rows of required data matrix are in text file attached.Please find the attached. (and the data need not be in that order).

But required matrix should be a "256x4 Complex double" having all rows unique.Any help ?

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Answer 1

Jos (10584) 2013-10-12

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p = [ 1 -1 j -j ] ;
[a,b,c,d] = ndgrid(p) ;
M = [a(:) b(:) c(:) d(:)]

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a 2013-10-14

Thank you Jos (10584).

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Answer 2

Sean de Wolski 2013-10-11

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[xx,yy,zz,qq] = ndgrid('1234');
V = [xx(:) yy(:) xx(:) qq(:)]

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Cedric 2013-10-12

编辑：Cedric 2013-10-12

在 MATLAB Online 中打开

@Sean: I don't think that it works as expected..

 >> size(unique(V, 'rows'))
 ans =
    64     4

a 2013-10-12

编辑：a 2013-10-12

@cedric

yeah.

All rows are not unique.

In my case it should be all unique rows and matrix size should be 256x4 complex double.

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Answer 3

Cedric 2013-10-12

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编辑：Cedric 2013-10-12

在 MATLAB Online 中打开

I guess that the following would work. I didn't think too much about it though and there must be a simpler or even trivial solution..

 >> ID = mod(floor((0:255).' * 2.^[0:-2:-6]), 4) + 1 ;
 >> p(ID)

Check

 >> size(unique(ID, 'rows'))
 ans =
   256     4

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a 2013-10-12

@cedric:

thank you for your answer but yeah you are right that there must be a simpler or even trivial solution.

Cedric 2013-10-12

编辑：Cedric 2013-10-12

Just in case nobody proposes a better solution, the way this one works is comparable to the way you build tables of binary codes.. you build the first column as 01010101.., the second as 0011001100.., the third as 000011110000.., and so on. My solution does the same in base 4.

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