1) Always state which version of Mathcad your question relates to.
2) Attaching a worksheet isusuallypreferable
What exactly do you mean by "eliminate"? Replace the non-real values by something else (their real part, their absolute value, NaN, a text string, ..." or is the new vector supposed to be smaller and just containing the real values from the original vector in the same order. We are talking about n x 1 matrices, right?