# How do I plot the magnitude of a complex-valued function?

My script is like this

```
v = var('v')
```

` `assume(v,'complex')

G = matrix([[0,1,0,0],[-v,1-v,0,0],[0,-v,1-v,0],[0,0,1,0]])

eigs = G.eigenvalues()

f1(v) = abs(eigs[0])

plot(f1,(-1,7))

```
The first eigenvalue is complex in a certain region and real elsewhere.
But it does not plot those portions of the plot where the eigenvalue becomes complex. What gives?
```

My plot is broken where the eigenvalue is complex, with the error:

verbose 0 (2717: plot.py, generate_plot_points) WARNING: When plotting, failed to evaluate function at 140 points. verbose 0 (2717: plot.py, generate_plot_points) Last error message: 'math domain error'

What I want to do is observe the behavior of the magnitude of the eigenvalue with respect to v, irrespective of whether the eigenvalue is real or complex.

If I try
```
G = matrix(CC, [[0,1,0,0],[-v,1-v,0,0],[0,-v,1-v,0],[0,0,1,0]])
```

, I get an error.