Systematically add entries to vector array

Hi,

Given I have a vector as for instance: [ 1 3 5 7 1 3 ...]

I want to add twice the number "8" after each entry, hence we would have:

[ 1 8 8 3 8 8 5 8 8 7 8 8 1 8 8 3 8 8 ...]

How could I do that, in a way which would be not specific for the length of my initial array? Thanks

Answer 1

[Stephen23]

Here is one efficient method, without creating any temporary variables:

>> V = [1 3 5 7 1 3];
>> V(2:3,:) = 8;
>> V(:).'
ans =
   1   8   8   3   8   8   5   8   8   7   8   8   1   8   8   3   8   8

Answer 2

[KSSV]

   A = [ 1 3 5 7 1 3] ;
   N = (length(A))*2+length(A) ;

C = 8*ones(N,1) ;
C(1:3:end) = A ;

[José-Luis]

 N = (length(A))*2+length(A) ;

What's wrong with length(A) .* 3?

:)