8000 DOC improve iris example (#26973) · scikit-learn/scikit-learn@a31e108 · GitHub
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eguentherElisabeth Güntherglemaitre
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DOC improve iris example (#26973)
Co-authored-by: Elisabeth Günther <eguenther@MacBook-Pro-von-Elisabeth.local> Co-authored-by: Guillaume Lemaitre <g.lemaitre58@gmail.com>
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‎examples/datasets/plot_iris_dataset.py

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"""
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=========================================================
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================
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The Iris Dataset
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=========================================================
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================
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This data sets consists of 3 different types of irises'
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(Setosa, Versicolour, and Virginica) petal and sepal
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length, stored in a 150x4 numpy.ndarray
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# Modified for documentation by Jaques Grobler
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# License: BSD 3 clause
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import matplotlib.pyplot as plt
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# unused but required import for doing 3d projections with matplotlib < 3.2
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import mpl_toolkits.mplot3d # noqa: F401
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# %%
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# Loading the iris dataset
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# ------------------------
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from sklearn import datasets
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from sklearn.decomposition import PCA
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# import some data to play with
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iris = datasets.load_iris()
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X = iris.data[:, :2] # we only take the first two features.
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y = iris.target
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x_min, x_max = X[:, 0].min() - 0.5, X[:, 0].max() + 0.5
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y_min, y_max = X[:, 1].min() - 0.5, X[:, 1].max() + 0.5
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plt.figure(2, figsize=(8, 6))
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plt.clf()
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# %%
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# Scatter Plot of the Iris dataset
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# --------------------------------
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import matplotlib.pyplot as plt
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_, ax = plt.subplots()
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scatter = ax.scatter(iris.data[:, 0], iris.data[:, 1], c=iris.target)
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ax.set(xlabel=iris.feature_names[0], ylabel=iris.feature_names[1])
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_ = ax.legend(
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scatter.legend_elements()[0], iris.target_names, loc="lower right", title="Classes"
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)
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# Plot the training points
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plt.scatter(X[:, 0], X[:, 1], c=y, cmap=plt.cm.Set1, edgecolor="k")
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plt.xlabel("Sepal length")
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plt.ylabel("Sepal width")
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# %%
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# Each point in the scatter plot refers to one of the 150 iris flowers
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# in the dataset, with the color indicating their respective type
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# (Setosa, Versicolour, and Virginica).
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# You can already see a pattern regarding the Setosa type, which is
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# easily identifiable based on its short and wide sepal. Only
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# considering these 2 dimensions, sepal width and length, there's still
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# overlap between the Versicolor and Virginica types.
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# %%
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# Plot a PCA representation
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# -------------------------
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# Let's apply a Principal Component Analysis (PCA) to the iris dataset
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# and then plot the irises across the first three PCA dimensions.
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# This will allow us to better differentiate between the three types!
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plt.xlim(x_min, x_max)
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plt.ylim(y_min, y_max)
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plt.xticks(())
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plt.yticks(())
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# unused but required import for doing 3d projections with matplotlib < 3.2
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import mpl_toolkits.mplot3d # noqa: F401
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from sklearn.decomposition import PCA
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# To getter a better understanding of interaction of the dimensions
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# plot the first three PCA dimensions
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fig = plt.figure(1, figsize=(8, 6))
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ax = fig.add_subplot(111, projection="3d", elev=-150, azim=110)
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X_reduced[:, 0],
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X_reduced[:, 1],
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X_reduced[:, 2],
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c=y,
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cmap=plt.cm.Set1,
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edgecolor="k",
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c=iris.target,
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s=40,
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)
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ax.set_title("First three PCA directions")
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ax.set_xlabel("1st eigenvector")
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ax.set_title("First three PCA dimensions")
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ax.set_xlabel("1st Eigenvector")
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ax.xaxis.set_ticklabels([])
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ax.set_ylabel("2nd eigenvector")
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ax.set_ylabel("2nd Eigenvector")
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ax.yaxis.set_ticklabels([])
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ax.set_zlabel("3rd eigenvector")
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ax.set_zlabel("3rd Eigenvector")
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ax.zaxis.set_ticklabels([])
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plt.show()
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# %%
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# PCA will create 3 new features that are a linear combination of the
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# 4 original features. In addition, this transform maximizes the variance.
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# With this transformation, we see that we can identify each species using
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# only the first feature (i.e. first eigenvalues).

‎sklearn/datasets/_base.py

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@@ -667,6 +667,9 @@ def load_iris(*, return_X_y=False, as_frame=False):
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array([0, 0, 1])
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>>> list(data.target_names)
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['setosa', 'versicolor', 'virginica']
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See :ref:`sphx_glr_auto_examples_datasets_plot_iris_dataset.py` for a more
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detailed example of how to work with the iris dataset.
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"""
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data_file_name = "iris.csv"
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data, target, target_names, fdescr = load_csv_data(

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