I'm trying to solve an optimization problem on the form
$$ min_x x^{\top}Cx $$
Subject to
$$ \mu^{\top}x \geq r $$ $$ x_j\geq0 $$ $$ 0.75 \leq \sum_{j=1}^n x_j \leq 1 $$
So far, I know what to do and how to do it. However, I want to extend the conditions with a condition of "if $x_j > 0$ then $x_j \geq v_j$". I.e., $x_j$ can be zero, but if it is not it must be greater than some other constant. Is this possible to express in the matrix form of the standard QP such that it can be used as a parameter of MatLabs quadprog or Rs solve.QP, and, if so, how would one go about doing it?