positive solutions error when solving eqn

Solving for how the error below can be solved:

syms y
x = 0.001;
z = 0.0009;
eqn = y^3 - 3*x*y + 3*z*x == 0
Sol_z = solve(eqn,y,'Real',true)

Sol_z =
 
 9.0024e-04
     0.0543
    -0.0552
 
%here I can not get the only positive solutions that I want (i.e. 0.054 and 9.0024e-04)
if (Sol_z > 0)
  b = Sol_z
end

"Conversion to logical from sym is not possible."

how can i solve this error and get the only positive solutions using the code above

Answer 1

[madhan ravi]

 Sol_z(double(Sol_z) > 0)