How to add zeros to the end of an array

I have two arrays like A=[ 1 5 3 8 9 4 7 6 5 2 ] & B=[ 5 2 3 9 7 4 5 ]

In 'A', I have 10 elements(say m) and in 'B', I have 7(say n) elements. I need to add 10-7=3 (m-n) zeros to the end of B.

Please help.

[Becky CNS]

I am trying to do this but with A and B as matrices. The error message I get is 'Dimensions of matrices being concatenated are not consistent'. All I want to do is add zeros to another vector the length of A-B. How would I change the above code?

[Jan]

If you post your code, we could fix it directly. This would be more convenient and useful than to create an artificial example.

A = rand(3,4);
B = rand(2,2);
B(size(A,1), size(A,2)) = 0;
A - B

Answer 1

[Jan]

Matlab fills missing elements with 0 automatically:

A = [1 5 3 8 9 4 7 6 5 2];
B = [5 2 3 9 7 4 5];
B(numel(A)) = 0;

Less efficient, but working also:

B = [B, zeros(1, length(A) - length(B))];

[Azzi Abdelmalek]

What if A and B have the same size? (for the first code)

[Jan]

In the OP's problem, the sizes of A and B are 10 and 7. For more general problems:

nA = numel(A);
nB = numel(B);
if nA > nB
  B(nA) = 0;
elseif nB > nA
  A(nB) = 0;
end

[Mori]

This adds zero at the end, what if we need first zeros and then elements of B?

[Andrei Bobrov]

B = [zeros(1, length(A) - length(B)), B];

[Mori]

this command works perfectly for raw array but not for column, any idea?

[Mori]

B=[zeros(length(A) - length(B),1);B]

[John Lutz]

Thanks Andrei Bobrov,for

B = [zeros(1, length(A) - length(B)), B];

this worked perfectly for me. Maybe someone will see this and provide an explanation! I couldnt make sense of it from the matlab zero doc

[Jan]

@John Lutz: zeros(1,n) creates a row vector of n zeros. [z,B] concatenates the arrays z and B horizontally. length(A)-length(B) determines the difference of the lengths of the two arrays.

[Black4Ghost]

I am sorry I am commenting so late on this Thread but I have the same Issue with the only difference that I don't want zeros to fill out my cell array. I want it filled out with chars of the value '0'. Also sorry for not opening a new question but its almost the same problem I am afraid.

[kay Dee]

thx worked for me

[Md Rezaul Karim]

Thank you Jan

[Jan]

@Black4Ghost: Filling with characters works by:

[YourData, rempmat('0', 1, wantedWidth - numel(YourData))]

Answer 2

[Azzi Abdelmalek]

A=[ 1 5 3 8 9 4 7 6 5 2 ];
B=[ 5 2 3 9 7 4 5 ];
B(end:numel(A))=0

[Jan]

B(end) overwrites the last element of B.

[Azzi Abdelmalek]

B(end+1:numel(A))=0

Answer 3

[Mohammad Sohail Khan]

Thank You

Answer 4

[Steven Lord]

If you're using release R2023b or later, you could use paddata or resize to do this.

A=[ 1 5 3 8 9 4 7 6 5 2 ];
B=[ 5 2 3 9 7 4 5 ];
n = max(length(A), length(B)); % using length is okay since A and B are both vectors

If we always want to make the vector longer or keep it the same size, use paddata.

A2 = paddata(A, n)

A2 = 1×10

1 5 3 8 9 4 7 6 5 2

B2 = paddata(B, n)

B2 = 1×10

5 2 3 9 7 4 5 0 0 0

If you want to append to the vector or remove elements depending on whether it's shorter or longer than your desired size, use resize.

A3 = resize(A, 8) % drop last 2 elements

A3 = 1×8

1 5 3 8 9 4 7 6

B3 = resize(B, 8) % add one 0 at the end

B3 = 1×8

5 2 3 9 7 4 5 0

There's also trimdata to always make it the desired length or shorter.