I'm new to MATLAB and this website as well. I tried searching for this question, but to no avail (so I apologize if this ends up being a questions which has already been asked here before). In class, we were assigned a problem with the following description: "For an n-dimensional vector X, the function should return another 2n-dimension where each element is repeated twice. For example: if a=[2 3 4 5], after using the function, a=[2 2 3 3 4 4 5 5];" It should work with a vector of ANY random size.
Your help is really appreciated! Thanks
use kron:
K = kron(X,Y) returns the Kronecker tensor product of X and Y. The result is a large array formed by taking all possible products between the elements of X and those of Y. If X is m-by-n and Y is p-by-q, then kron(X,Y) is m*p-by-n*q.
In your case:
kron(a,[1 1])
will give you what you wanted
Some alternatives answers for your question:
reshape([a ; a],1,[])
reshape([a'*[1 1]]',1,[])
来源：https://stackoverflow.com/questions/17509090/matlab-duplicate-each-element-of-a-vector