Q: How to plot the phase portrait for $4\times 4$ ODE system? I wrote below the instructions in Mathematica because I wanted to see the phase portrait of systems of DE of $4\times 4$ dimension. But Mathematica cannot recognize the last 2 variables $y$ and $z$ and marks an error.
What can I do to solve this problem?
StreamPlot[{b n - d w - w β x - w β1 y,
            β w x - x (d - c - γ),
            β1 w y - (d + c1 + γ1) y,
            γ x + γ1 y - d z},
  {w, -5, 5}, {x, -5, 5}, {y, -5, 5}, {z, -5, 5}]

