Sparse vector transpose is slow

I'm performing the operation

X = [X; x']

in my MATLAB code. x is a very large and very sparse vector which is created as a column vector

x = sparse(nonZeroRows, 1, vals, vectorLength, 1);

The problem is that taking the transpose x' is VERY slow. Also, creating x' directly through

xT = sparse(1, nonZeroRows, vals, 1, vectorLength);

is also very slow.

How can I perform this operation efficiently?

[Walter Roberson]

I am not surprised at it being slow; sparse vectors are organized by columns (I think it was), one header per column used, so when you transpose to a row it has to create headers for each of those rows.

I do not know what (if anything) can be done to improve the situation.