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"""
============================
Create an imbalanced dataset
============================
An illustration of the :func:`~imblearn.datasets.make_imbalance` function to
create an imbalanced dataset from a balanced dataset. We show the ability of
:func:`~imblearn.datasets.make_imbalance` of dealing with Pandas DataFrame.
"""
# Authors: Dayvid Oliveira
# Christos Aridas
# Guillaume Lemaitre <g.lemaitre58@gmail.com>
# License: MIT
# %%
print(__doc__)
import seaborn as sns
sns.set_context("poster")
# %% [markdown]
# Generate the dataset
# --------------------
#
# First, we will generate a dataset and convert it to a
# :class:`~pandas.DataFrame` with arbitrary column names. We will plot the
# original dataset.
# %%
import matplotlib.pyplot as plt
import pandas as pd
from sklearn.datasets import make_moons
X, y = make_moons(n_samples=200, shuffle=True, noise=0.5, random_state=10)
X = pd.DataFrame(X, columns=["feature 1", "feature 2"])
ax = X.plot.scatter(
x="feature 1",
y="feature 2",
c=y,
colormap="viridis",
colorbar=False,
)
sns.despine(ax=ax, offset=10)
plt.tight_layout()
# %% [markdown]
# Make a dataset imbalanced
# -------------------------
#
# Now, we will show the helpers :func:`~imblearn.datasets.make_imbalance`
# that is useful to random select a subset of samples. It will impact the
# class distribution as specified by the parameters.
# %%
from collections import Counter
def ratio_func(y, multiplier, minority_class):
target_stats = Counter(y)
return {minority_class: int(multiplier * target_stats[minority_class])}
# %%
from imblearn.datasets import make_imbalance
fig, axs = plt.subplots(nrows=2, ncols=3, figsize=(15, 10))
X.plot.scatter(
x="feature 1",
y="feature 2",
c=y,
ax=axs[0, 0],
colormap="viridis",
colorbar=False,
)
axs[0, 0].set_title("Original set")
sns.despine(ax=axs[0, 0], offset=10)
multipliers = [0.9, 0.75, 0.5, 0.25, 0.1]
for ax, multiplier in zip(axs.ravel()[1:], multipliers):
X_resampled, y_resampled = make_imbalance(
X,
y,
sampling_strategy=ratio_func,
**{"multiplier": multiplier, "minority_class": 1},
)
X_resampled.plot.scatter(
x="feature 1",
y="feature 2",
c=y_resampled,
ax=ax,
colormap="viridis",
colorbar=False,
)
ax.set_title(f"Sampling ratio = {multiplier}")
sns.despine(ax=ax, offset=10)
plt.tight_layout()
plt.show()
|
