# Plotting in `giotto-tda`

¶

`giotto-tda`

includes a set of plotting functions and class methods,
powered by `plotly`

. The library’s plotting API is designed to
facilitate the exploration of intermediate results in pipelines by
harnessing the highly visual nature of topological signatures.

This notebook is a quick tutorial on how to use `giotto-tda`

’s
plotting functionalities and unified plotting API. The plotting
functions in `gtda.mapper`

are not covered here as they are somewhat
tailored to the Mapper algorithm, see the dedicated
tutorial.

If you are looking at a static version of this notebook and would like to run its contents, head over to github.

**License: AGPLv3**

## 1. Basic philosophy and `plot`

methods¶

The computational building blocks of `giotto-tda`

are
`scikit-learn`

–style estimators. Typically, they are also
transformers, i.e. they possess a `transform`

and/or a
`fit-transform`

method which:

act on an array-like object

`X`

which collects a certain number of “samples” of a given kind;return a transformed array-like object

`Xt`

which collects a (potentially different) number of “samples” of a potentially different kind.

The basic philosophy of `giotto-tda`

’s class-level plotting API is
to equip relevant transformers with `plot`

methods taking two main
arguments:

an object such as

`Xt`

above (i.e. consistent with the*outputs*of`transform`

or`fit-transform`

);an integer index passed via the

`sample`

keyword and indicating which sample in`Xt`

should be plotted.

In other words, `<transformer>.plot(Xt, sample=i)`

will produce a plot
of `Xt[i]`

which is tailored to the nature of the samples in `Xt`

.

### 1.1 Plotting functions¶

Several `plot`

methods in `giotto-tda`

actually fall back to
specialised functions which can be found in the plotting
subpackage
and which can be used directly instead. However, unless the additional
degree of control is necessary, `plot`

methods should be preferred as
they often exploit class parameters and/or attributes (e.g. those
computed during `fit`

) to automatically fill some parameters in the
corresponding functions.

### 1.2 Example: Plotting persistence diagrams with `VietorisRipsPersistence`

¶

Let’s take the example of `VietorisRipsPersistence`

– a transformer
also covered in another
notebook.
Let’s create the input collection `X`

for this transformer as a
collection of randomly generated point clouds, each containing 100
points positioned along two circles.

```
import numpy as np
np.random.seed(seed=42)
from gtda.homology import VietorisRipsPersistence
from sklearn.datasets import make_circles
X = np.asarray([
make_circles(100, factor=np.random.random())[0]
for i in range(10)
])
```

Incidentally, samples in `X`

can be plotted using
`gtda.plotting.plot_point_cloud`

.

```
from gtda.plotting import plot_point_cloud
i = 0
plot_point_cloud(X[i])
```