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  plotly:
    description: How to make a dendrogram in Python with Plotly.
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---

#### Basic Dendrogram

A [dendrogram](https://en.wikipedia.org/wiki/Dendrogram) is a diagram representing a tree. The [figure factory](/python/figure-factories/) called `create_dendrogram` performs [hierarchical clustering](https://en.wikipedia.org/wiki/Hierarchical_clustering) on data and represents the resulting tree. Values on the tree depth axis correspond to distances between clusters.

Dendrogram plots are commonly used in computational biology to show the clustering of genes or samples, sometimes in the margin of heatmaps.

```python
import plotly.figure_factory as ff
import numpy as np
np.random.seed(1)

X = np.random.rand(15, 12) # 15 samples, with 12 dimensions each
fig = ff.create_dendrogram(X)
fig.update_layout(width=800, height=500)
fig.show()
```

#### Set Color Threshold

```python
import plotly.figure_factory as ff

import numpy as np

X = np.random.rand(15, 10) # 15 samples, with 10 dimensions each
fig = ff.create_dendrogram(X, color_threshold=1.5)
fig.update_layout(width=800, height=500)
fig.show()
```

#### Set Orientation and Add Labels

```python
import plotly.figure_factory as ff

import numpy as np

X = np.random.rand(10, 12)
names = ['Jack', 'Oxana', 'John', 'Chelsea', 'Mark', 'Alice', 'Charlie', 'Rob', 'Lisa', 'Lily']
fig = ff.create_dendrogram(X, orientation='left', labels=names)
fig.update_layout(width=800, height=800)
fig.show()
```

#### Plot a Dendrogram with a Heatmap

This example uses randomly generated sample data to demonstrate how to plot a dendrogram with a heatmap.

```python
import plotly.graph_objects as go
import plotly.figure_factory as ff

import numpy as np
from scipy.spatial.distance import pdist, squareform


# Generate sample data
np.random.seed(1)
X = np.random.rand(15, 15)
labels = [f'Sample_{i}' for i in range(15)]
data_array = X

# Initialize figure by creating upper dendrogram
fig = ff.create_dendrogram(data_array, orientation='bottom', labels=labels)
for i in range(len(fig['data'])):
    fig['data'][i]['yaxis'] = 'y2'

# Create Side Dendrogram
dendro_side = ff.create_dendrogram(data_array, orientation='right')
for i in range(len(dendro_side['data'])):
    dendro_side['data'][i]['xaxis'] = 'x2'

# Add Side Dendrogram Data to Figure
for data in dendro_side['data']:
    fig.add_trace(data)

# Create Heatmap
dendro_leaves = dendro_side['layout']['yaxis']['ticktext']
dendro_leaves = list(map(int, dendro_leaves))
data_dist = pdist(data_array)
heat_data = squareform(data_dist)
heat_data = heat_data[dendro_leaves,:]
heat_data = heat_data[:,dendro_leaves]

heatmap = [
    go.Heatmap(
        x = dendro_leaves,
        y = dendro_leaves,
        z = heat_data,
        colorscale = 'Blues'
    )
]

heatmap[0]['x'] = fig['layout']['xaxis']['tickvals']
heatmap[0]['y'] = dendro_side['layout']['yaxis']['tickvals']

# Add Heatmap Data to Figure
for data in heatmap:
    fig.add_trace(data)

# Edit Layout
fig.update_layout({'width':800, 'height':800,
                         'showlegend':False, 'hovermode': 'closest',
                         })
# Edit xaxis
fig.update_layout(xaxis={'domain': [.15, 1],
                                  'mirror': False,
                                  'showgrid': False,
                                  'showline': False,
                                  'zeroline': False,
                                  'ticks':""})
# Edit xaxis2
fig.update_layout(xaxis2={'domain': [0, .15],
                                   'mirror': False,
                                   'showgrid': False,
                                   'showline': False,
                                   'zeroline': False,
                                   'showticklabels': False,
                                   'ticks':""})

# Edit yaxis
fig.update_layout(yaxis={'domain': [0, .85],
                                  'mirror': False,
                                  'showgrid': False,
                                  'showline': False,
                                  'zeroline': False,
                                  'showticklabels': False,
                                  'ticks': ""
                        })
# Edit yaxis2
fig.update_layout(yaxis2={'domain':[.825, .975],
                                   'mirror': False,
                                   'showgrid': False,
                                   'showline': False,
                                   'zeroline': False,
                                   'showticklabels': False,
                                   'ticks':""})

# Plot!
fig.show()
```

### Reference

For more info on `ff.create_dendrogram()`, see the [full function reference](https://plotly.com/python-api-reference/generated/plotly.figure_factory.create_dendrogram.html)
