how to create a vector A [1,1,2,2,3,3] from a vector B [1,2,3]

how to create a vector A [1,1,2,2,3,3] from a vector B[1,2,3] using a function

Answer 1

[John D'Errico]

help repelem

 REPELEM Replicate elements of an array.
    U = REPELEM(V,N), where V is a vector, returns a vector of repeated
    elements of V.
    - If N is a scalar, each element of V is repeated N times.
    - If N is a vector, element V(i) is repeated N(i) times. N must be the
      same length as V.
 
    B = repelem(A, R1, ..., RN), returns an array with each element of A
    repeated according to R1, ..., RN. Each R1, ..., RN must either be a
    scalar or a vector with the same length as A in the corresponding
    dimension.
 
    Example: If A = [1 2; 3 4], then repelem(A, 2, 3) returns a matrix 
    containing a 2-by-3 block of each element of A:
    [1 1 1 2 2 2; ...
     1 1 1 2 2 2; ...
     3 3 3 4 4 4; ...
     3 3 3 4 4 4].
 
    See also REPMAT, BSXFUN, MESHGRID.

    Documentation for repelem
       doc repelem

    Other functions named repelem

       codistributed/repelem    symfun/repelem     tall/repelem
       gpuArray/repelem         tabular/repelem