# `analyze.spectrogram`

The function [`analyze.spectrogram`](#digger.analyze.spectrogram.spectrogram) analyzes a numerical gauge trace using a fast Fourier transform to generate a spectrogram.

```{literalinclude} ../../../../../examples/post-run/barry_arm/setpostprocess.py
:language: python
:start-after: Block 5 Start
:end-before: Block 5 End
```

:::{attention}
This code snippet is not fully self-sufficient. This snippet relies on simulation output files. To reproduce the example, execute the file `digger/examples/post-run/barry_arm/setpostprocess.py` from within the directory in which it is located. **Before** the script is executed either the example simulation must be run or the file `digger/data/barry_arm_output.zip` must be unzipped and the resulting directory (`_output`) must be placed within `digger/examples/post-run/barry_arm/`.
:::

The utility function [`digger.utils.gauge2ts`](#digger.utils.gauge2ts.gauge2ts) assists in ensuring that the numerical gauge data provided by D-Claw conforms to the expectations of the spectrogram and [wavelet analysis](example-wavelet).

Running this code snippet generates three diagnostic figures that depict the detrended gauge, the frequency content of the gauge trace, and the spectrogram.

```{figure} ../../../../_static/from_examples/spectrum-BA_timeseries.png
:alt: Example digger.analyze.spectrogram gauge figure.

An example of the diagnostic output provided by digger.analyze.spectrogram showing the detrended gauge trace.
```

```{figure} ../../../../_static/from_examples/spectrum-BA_fourier.png
:alt: Example digger.analyze.spectrogram fourier transform figure.

An example of the diagnostic output provided by digger.analyze.spectrogram showing the frequency content.
```

```{figure} ../../../../_static/from_examples/spectrum-BA_spectrogram.png
:alt: Example digger.analyze.spectrogram spectrogram figure.

An example of the diagnostic output provided by digger.analyze.spectrogram showing the spectrogram.
```