Insert Zeros (m -rows) in an existing Matrix every n-rows in an efficient way

I've data like this (the actualy matrix is much bigger)

A =

     1     1
     2     2
     3     3
     4     4
     5     5
     6     6
     7     7
     8     8
     9     9
    10    10
    11    11
    12    12

Let's say I want to insert 2 rows of zeros (m=2, zeros(2,2)) every 3 lines (n=3), so that the result would be:

A =

     1     1
     2     2
     3     3
     0     0
     0     0
     4     4
     5     5
     6     6     
     0     0
     0     0
     7     7
     8     8
     9     9
     0     0
     0     0
    10    10     
    11    11
    12    12
     0    0
     0    0

Is there a quick way to do it? Online I found the "insertrows"-function but that didn't work... Thanks a lot in advance!

Answer 1

[Azzi Abdelmalek]

[n,m]=size(A)
B=permute(reshape(A',m,3,[]),[2 1 3]);
p=size(B,3)
C=[B;zeros(2,m,p)]
out=reshape( C(:,:),[],m,1)

[Tim]

perfect! Thanks a lot

[Jorge Ignacio Cisneros Saldana]

The result is wrong

1 7 2 8 3 9 0 0 0 0 1 7 2 8 3 9 0 0 0 0 4 10 5 11 6 12 0 0 0 0 4 10 5 11 6 12 0 0 0 0

Answer 2

[Andrei Bobrov]

m = 3;
k = 2;

n = size(A);
out = reshape([reshape(A,m,[]);zeros(k,n(1)/m*n(2))],[],n(2));

or

m = 3;
k = 2;

n = size(A);
c = ones(1,n(2));
t = rem((0:n(1)*(k/m+1)-1)',m+k)+1 <= m;
out = t*c
out(t(:,c)) = A;

[Jorge Ignacio Cisneros Saldana]

Definitely works!! thanks

Answer 3

[Jos (10584)]

But you can use INSERTROWS:

% data
A = cumsum(ones(12,2),1) % as above
n = 3 ;
m = 2 ;

% engine
B = insertrows(A,0,repmat(n:n:size(A,1),m,1))

btw, I am the author of this function, so I might be a little biased ;-)

[Tim]

wow great, now it works, I didn't download the function before..thanks

[Jos (10584)]

The trick is to use the same insertion location multiple times. I acknowledge that this might be a little unclear when reading the documentation.

[Jorge Ignacio Cisneros Saldana]

It does not work error

Error in Insertzeros (line 30) B = insertrows(A,0,repmat(n:n:size(A,1),m,1));