# How to save Topology ¶

An introduction of how to save topology.

In this tutorial, we visualize iris dataset and save topology to image. you can learn following points.

- How to save topology.

## Requirements ¶

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```

```
from sklearn.datasets import load_iris
from renom_tda.topology import Topology
from renom_tda.lens import PCA
```

## Load dataset ¶

Next, we have to load iris dataset. To accomplish this, we'll use the
```
load_iris
```

module included in the scikit-learn package.

The iris dataset consists of 150 data and data has 4 columns.

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In [2]:
```

```
iris = load_iris()
data = iris.data
target = iris.target
```

## Load data ¶

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```

```
topology.load_data(data)
```

## Create point cloud ¶

Next, we create point cloud that is projected on 2 or 3 dimention space.

We use fit_transform function to project data with two parameter, metric and lens.

Metric is how to measure distance between data. Lens is the axis of projected space.

This tutorial use metric None and lens PCA. This means dimenstion reduction with normal PCA.

```
In [5]:
```

```
metric = None
lens = [PCA(components=[0, 1])]
topology.fit_transform(metric=metric, lens=lens)
```

## Mapping to topological space ¶

Next, we create topology.

We use map function to map point cloud to topological space.

We set three parameter, resolution, overlap, eps and min_samples.

Resolution means the number of division. It effects the number of nodes.

Overlap means the easiness to connect with each nodes.

Eps and min_samples is used by clustering method for data that is in nodes.

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In [6]:
```

```
topology.map(resolution=15, overlap=0.5, eps=0.1, min_samples=3)
```

```
created 69 nodes.
created 188 edges.
```

## Color topology ¶

Next, we colorize topology using color funcion.

In this tutorial, topology is colored by iris label values.

We can select color_method is "mean" or "mode" and color_type is "rgb" or "gray".

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```

```
topology.color(target, color_method="mode", color_type="rgb")
```

## Save topology ¶

Finally, we save topology.

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```

```
topology.save("test.png", fig_size=(10, 10), node_size=10, edge_width=2)
```

output file is follow.