increase the length of a martix every 5 rows

Question

antonet 2012-8-5

0
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https://ww2.mathworks.cn/matlabcentral/answers/45305-increase-the-length-of-a-martix-every-5-rows

Dear all,

I have a matrix (double array) of dimension 40000 by 7 and I want to increase the length of this matrix every 5 rows by adding a cell NaN.

For instance, if I have initially

 A=[2.4332    4.1477;
6073    4.5900;
2310    3.7442;
4555    4.1178;
5096    4.1946;
7517    4.7802;
8372    4.9423;
9577    5.1563;
2365    5.6061;
0658    5.3787;
9244    5.0497;
6104    4.4623;
5419    4.4164;
4947    4.3577;
5633    4.7050
  ]

then I want

 A=[2.4332    4.1477;
6073    4.5900;
2310    3.7442;
4555    4.1178;
5096    4.1946;
      NaN        NaN
7517    4.7802;
8372    4.9423;
9577    5.1563;
2365    5.6061;
0658    5.3787;
      NaN        NaN
9244    5.0497;
6104    4.4623;
5419    4.4164;
4947    4.3577;
5633    4.7050;
      NaN        NaN
  ]

I am looking for an efficient code (1-2 lines if possible)

thank you very much

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Answer 1

Oleg Komarov 2012-8-5

1
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https://ww2.mathworks.cn/matlabcentral/answers/45305-increase-the-length-of-a-martix-every-5-rows#answer_55469

在 MATLAB Online 中打开

The efficient code:

[r,c]       = size(A);
add         = floor(r/5);
Anew        = NaN(r + add,c);
idx         = (1:r) + reshape(repmat(0:add-1,5,1),1,r);
Anew(idx,:) = A;

The two line code:

Anew = NaN(size(A,1) + size(A,1)/5,size(A,2));
Anew((1:size(A,1)) + reshape(repmat(0:floor(size(A,1)/5)-1,5,1),1,size(A,1)),:) = A;

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Matt Fig 2012-8-5

编辑：Matt Fig 2012-8-5

在 MATLAB Online 中打开

I'll take a stab at it.

function Anew = insert_nansmatt(A,x)
% Insert a row of nans in A every x rows. 
% A need not have mod(size(A,1),x)==0.
[R,C] = size(A);
S = R + floor(R/x);
Anew = nan(S,C);
idx1 = true(S,1);
idx1(x+1:(x+1):S) = false;
Anew(idx1,:) = A;

Azzi Abdelmalek 2012-8-5

i like this one

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Answer 2

Azzi Abdelmalek 2012-8-5

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/45305-increase-the-length-of-a-martix-every-5-rows#answer_55470

编辑：Walter Roberson 2012-8-5

在 MATLAB Online 中打开

% this code is for test the example 
 B=reshape(A,5,2,3);B(6,:,:)=nan;result= reshape(B,18,2)
% this code is for your real data
 B=reshape(A,5,7,1400);B(6,:,:)=nan;result= reshape(B,8400,7)
% note that 1400 = 7000/5; and 8400=(5+1)*1400