# 1. Calculating and plotting a `FrequencySeries`

¶

The LIGO Laboratory has publicly released the strain data around the time of the GW150914 gravitational-wave detection; we can use these to calculate and display the spectral sensitivity of each of the detectors at that time.

In order to generate a `FrequencySeries`

we need to import the
`TimeSeries`

and use
`fetch_open_data()`

to download the strain
records:

```
from gwpy.timeseries import TimeSeries
lho = TimeSeries.fetch_open_data('H1', 1126259446, 1126259478)
llo = TimeSeries.fetch_open_data('L1', 1126259446, 1126259478)
```

We can then call the `asd()`

method to
calculated the amplitude spectral density for each
`TimeSeries`

:

```
lhoasd = lho.asd(4, 2)
lloasd = llo.asd(4, 2)
```

We can then `plot()`

the spectra using the ‘standard’
colour scheme:

```
plot = lhoasd.plot(label='LIGO-Hanford', color='gwpy:ligo-hanford')
ax = plot.gca()
ax.plot(lloasd, label='LIGO-Livingston', color='gwpy:ligo-livingston')
ax.set_xlim(10, 2000)
ax.set_ylim(5e-24, 1e-21)
ax.legend(frameon=False, bbox_to_anchor=(1., 1.), loc='lower right', ncol=2)
plot.show()
```

(`png`

)