Repeat rows in a matrix

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Tommaso Fornaciari
Tommaso Fornaciari on 16 Nov 2016
Answered: Changoleon on 16 Nov 2016
Hello, I have a 7832x20 matrix(A) and and I would like to create another identical sized matrix(B) where the first 22 rows of B are equal to the first row of A, the 23rd up to the 44th row of B to be equal to the 23rd row of A...rows 45 to 66 of B equal to row 45 and ,I think you got the point,until the last row. I have tried the following code but I get a dimension mismatch error
for mm=1:22:7832
B(mm,:) = padarray(A(mm,:),[21],'replicate','post')
Is there anotherway to do it? Am I completely off? I thank you in advance for your help

Answers (3)

Guillaume on 16 Nov 2016
B = repelem(A(1:22:end, :), 22, 1);
is all that is needed. repelem was introduced in R2015a.
Tommaso Fornaciari
Tommaso Fornaciari on 16 Nov 2016
worked! thank you. cheers
Image Analyst
Image Analyst on 16 Nov 2016
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Honglei Chen
Honglei Chen on 16 Nov 2016
B = kron(A(1:22:end,:),ones(22,1))

Changoleon on 16 Nov 2016
Hi, I got really really close to the answer. You just need to add 2 or 3 lines of code to finish it.
A = [ 1 2; 3 4; 5 6; 7 8; 9 10; 11 12; 13 14; 15 16; 17 18; 19 20];
for i = 1:2:10
B(i,:) = A(i,:);
for j=1:1:9
if B(j,1)==0
B(j,:) = B(j-1,:);


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