### Calculate Half-Value-Layer and Plot Spectrum with SpekPy

Source: https://github.com/spekpy/spekpy_release/blob/master/SpekPy-Notebook.ipynb

This snippet demonstrates how to import SpekPy and Matplotlib, create an x-ray spectrum, apply an aluminum filter, calculate the first half-value-layer, and plot the spectrum. Ensure SpekPy and Matplotlib are installed.

```python
import spekpy as sp
import matplotlib.pyplot as plt

s = sp.Spek(kvp=80,th=12)
s.filter('Al',4)

hvl = s.get_hvl1()
print(hvl,'mm')

k, f = s.get_spectrum(edges=True)

plt.plot(k, f)
plt.xlabel('Energy [keV]')
plt.ylabel('Fluence per mAs per unit energy [photons/cm2/mAs/keV]')
plt.title('An example x-ray spectrum')
plt.show()
```

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