(gallery_ecdf_pit)=

# PIT-ECDF

Faceted plot with PIT Δ-ECDF values for each variable

The ``plot_ecdf_pit`` function assumes the values passed to it has already been transformed
to PIT values, as in the case of SBC analysis or values from ``arviz_base.loo_pit``.

The distribution should be uniform if the model is well-calibrated.

To make the plot easier to interpret, we plot the Δ-ECDF, that is, the difference between
the expected CDF from the observed ECDF. As small deviations from uniformity are expected,
the plot also shows the credible envelope.



::::::{tab-set}
:class: full-width
:sync-group: backend

:::::{tab-item} Matplotlib
:sync: matplotlib

![Matplotlib version of plot_ecdf_pit](_images/plot_ecdf_pit.png)

:::::

:::::{tab-item} Bokeh
:sync: bokeh

```{bokeh-plot}
:source-position: none

from bokeh.plotting import show

from arviz_base import load_arviz_data

import arviz_plots as azp

azp.style.use("arviz-variat")

data = load_arviz_data("sbc")
pc = azp.plot_ecdf_pit(
data,
backend="bokeh"  # change to preferred backend
)


# for some reason the bokeh plot extension needs explicit use of show
show(pc.viz["figure"].item() if pc.viz["figure"].item() is not None else pc.viz["plot"].item())
```

Link to this page with the [bokeh tab selected](https://arviz-plots.readthedocs.io/en/latest//gallery/plot_ecdf_pit.html?backend=bokeh#synchronised-tabs)
:::::

:::::{tab-item} Plotly
:sync: plotly

```{jupyter-execute}
:hide-code:

from arviz_base import load_arviz_data

import arviz_plots as azp

azp.style.use("arviz-variat")

data = load_arviz_data("sbc")
pc = azp.plot_ecdf_pit(
data,
backend="plotly"  # change to preferred backend
)
pc.show()
```

Link to this page with the [plotly tab selected](https://arviz-plots.readthedocs.io/en/latest//gallery/plot_ecdf_pit.html?backend=plotly#synchronised-tabs)
:::::
::::::

```{literalinclude} _scripts/plot_ecdf_pit.py
:emphasize-lines: 10
```



:::{seealso}
API Documentation: {func}`~arviz_plots.plot_ecdf_pit`
:::



## Other examples with `plot_ecdf_pit`

```{eval-rst}
.. minigallery:: plot_ecdf_pit
```


:::{div} example-plot-download
{download}`Download Python Source Code: plot_ecdf_pit.py<_scripts/plot_ecdf_pit.py>`
:::