MATLAB: Matrix manipulation

matrix manipulation

Hi, I've an ASCII file like this

 450 1 2 3 4 5
 6 7 8 9 10 11
 12 13
 451 1 2 3 4 5
 6 7 8 9 10 11
 12 13
 452 1 2 3 4 5
 6 7 8 9 10 11
 12 13
 ...

and I would modify it to obtain a file like this

 450 1 2 3 4 5 6 7 8 9 10 11 12 13
 451 1 2 3 4 5 6 7 8 9 10 11 12 13
 452 1 2 3 4 5 6 7 8 9 10 11 12 13

Any suggestions? Thanks Gianluca

Best Answer

f = fopen('test.txt');
c = textscan(f,'%f');
fclose(f);
out = reshape(c{:},[],3)'

Related Solutions

MATLAB: How to flip every 5th row and column in matrix

>> M = repmat((1:12).',1,3)
M =
    1    1    1
    2    2    2
    3    3    3
    4    4    4
    5    5    5
    6    6    6
    7    7    7
    8    8    8
    9    9    9
   10   10   10
   11   11   11
   12   12   12
>> M([4:6:end,6:6:end],:) = M([6:6:end,4:6:end],:)
M =
    1    1    1
    2    2    2
    3    3    3
    6    6    6
    5    5    5
    4    4    4
    7    7    7
    8    8    8
    9    9    9
   12   12   12
   11   11   11
   10   10   10

MATLAB: Shift rows by different amounts

 N = 4 ;
 A = repmat( 1:N^2, N^2, 1 ) ; % Dummy example.
 for k  = 2 : N
    A(k:N:N^2,:) = circshift( A(k:N:N^2,:), (k-1) * N, 2 ) ;
 end

With that, the the original A is:

 A =
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16

and the final:

 A =
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
    13    14    15    16     1     2     3     4     5     6     7     8     9    10    11    12
     9    10    11    12    13    14    15    16     1     2     3     4     5     6     7     8
     5     6     7     8     9    10    11    12    13    14    15    16     1     2     3     4
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
    13    14    15    16     1     2     3     4     5     6     7     8     9    10    11    12
     9    10    11    12    13    14    15    16     1     2     3     4     5     6     7     8
     5     6     7     8     9    10    11    12    13    14    15    16     1     2     3     4
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
    13    14    15    16     1     2     3     4     5     6     7     8     9    10    11    12
     9    10    11    12    13    14    15    16     1     2     3     4     5     6     7     8
     5     6     7     8     9    10    11    12    13    14    15    16     1     2     3     4
     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16
    13    14    15    16     1     2     3     4     5     6     7     8     9    10    11    12
     9    10    11    12    13    14    15    16     1     2     3     4     5     6     7     8
     5     6     7     8     9    10    11    12    13    14    15    16     1     2     3     4

I am not sure that the solutions that don't involve a FOR loop are more efficient ultimately, because the FOR loop has only N-1 iterations and no realloc or conversion to/from cell arrays. You'd have to profile every approach to be sure.

Best Answer

Related Solutions

MATLAB: How to flip every 5th row and column in matrix

MATLAB: Shift rows by different amounts

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