Note

Click here to download the full example code

# Scatter plot with histograms¶

Show the marginal distributions of a scatter as histograms at the sides of the plot.

For a nice alignment of the main axes with the marginals, two options are shown below.

- the axes positions are defined in terms of rectangles in figure coordinates
- the axes positions are defined via a gridspec

An alternative method to produce a similar figure using the `axes_grid1`

toolkit is shown in the
Scatter Histogram (Locatable Axes) example.

Let us first define a function that takes x and y data as input, as well as three axes, the main axes for the scatter, and two marginal axes. It will then create the scatter and histograms inside the provided axes.

```
import numpy as np
import matplotlib.pyplot as plt
# Fixing random state for reproducibility
np.random.seed(19680801)
# some random data
x = np.random.randn(1000)
y = np.random.randn(1000)
def scatter_hist(x, y, ax, ax_histx, ax_histy):
# no labels
ax_histx.tick_params(axis="x", labelbottom=False)
ax_histy.tick_params(axis="y", labelleft=False)
# the scatter plot:
ax.scatter(x, y)
# now determine nice limits by hand:
binwidth = 0.25
xymax = max(np.max(np.abs(x)), np.max(np.abs(y)))
lim = (int(xymax/binwidth) + 1) * binwidth
bins = np.arange(-lim, lim + binwidth, binwidth)
ax_histx.hist(x, bins=bins)
ax_histy.hist(y, bins=bins, orientation='horizontal')
```

## Axes in figure coordinates¶

To define the axes positions, `Figure.add_axes`

is provided with a rectangle
`[left, bottom, width, height]`

in figure coordinates. The marginal axes
share one dimension with the main axes.

```
# definitions for the axes
left, width = 0.1, 0.65
bottom, height = 0.1, 0.65
spacing = 0.005
rect_scatter = [left, bottom, width, height]
rect_histx = [left, bottom + height + spacing, width, 0.2]
rect_histy = [left + width + spacing, bottom, 0.2, height]
# start with a square Figure
fig = plt.figure(figsize=(8, 8))
ax = fig.add_axes(rect_scatter)
ax_histx = fig.add_axes(rect_histx, sharex=ax)
ax_histy = fig.add_axes(rect_histy, sharey=ax)
# use the previously defined function
scatter_hist(x, y, ax, ax_histx, ax_histy)
plt.show()
```

## Using a gridspec¶

We may equally define a gridspec with unequal width- and height-ratios to achieve desired layout. Also see the Customizing Figure Layouts Using GridSpec and Other Functions tutorial.

```
# start with a square Figure
fig = plt.figure(figsize=(8, 8))
# Add a gridspec with two rows and two columns and a ratio of 2 to 7 between
# the size of the marginal axes and the main axes in both directions.
# Also adjust the subplot parameters for a square plot.
gs = fig.add_gridspec(2, 2, width_ratios=(7, 2), height_ratios=(2, 7),
left=0.1, right=0.9, bottom=0.1, top=0.9,
wspace=0.05, hspace=0.05)
ax = fig.add_subplot(gs[1, 0])
ax_histx = fig.add_subplot(gs[0, 0], sharex=ax)
ax_histy = fig.add_subplot(gs[1, 1], sharey=ax)
# use the previously defined function
scatter_hist(x, y, ax, ax_histx, ax_histy)
plt.show()
```

References

The use of the following functions, methods, classes and modules is shown in this example:

**Total running time of the script:** ( 0 minutes 1.996 seconds)

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