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Pushing the docs to dev/ for branch: master, commit f43dd0e650bcc5a200a5b9b5ea57a6dd09f3f2ce
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dev/_downloads/plot_missing_values.ipynb

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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"\n# Imputing missing values before building an estimator\n\n\nMissing values can be replaced by the mean, the median or the most frequent\nvalue using the basic ``SimpleImputer``.\nThe median is a more robust estimator for data with high magnitude variables\nwhich could dominate results (otherwise known as a 'long tail').\n\nAnother option is the MICE imputer. This uses round-robin linear regression,\ntreating every variable as an output in turn. The version implemented assumes\nGaussian (output) variables. If your features are obviously non-Normal,\nconsider transforming them to look more Normal so as to improve performance.\n\n"
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"\n# Imputing missing values before building an estimator\n\n\nMissing values can be replaced by the mean, the median or the most frequent\nvalue using the basic ``SimpleImputer``.\nThe median is a more robust estimator for data with high magnitude variables\nwhich could dominate results (otherwise known as a 'long tail').\n\nAnother option is the ``ChainedImputer``. This uses round-robin linear\nregression, treating every variable as an output in turn. The version\nimplemented assumes Gaussian (output) variables. If your features are obviously\nnon-Normal, consider transforming them to look more Normal so as to improve\nperformance.\n\n"
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]
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{
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},
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"outputs": [],
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"source": [
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"import numpy as np\nimport matplotlib.pyplot as plt\n\nfrom sklearn.datasets import load_diabetes\nfrom sklearn.datasets import load_boston\nfrom sklearn.ensemble import RandomForestRegressor\nfrom sklearn.pipeline import Pipeline\nfrom sklearn.impute import SimpleImputer, MICEImputer\nfrom sklearn.model_selection import cross_val_score\n\nrng = np.random.RandomState(0)\n\n\ndef get_results(dataset):\n X_full, y_full = dataset.data, dataset.target\n n_samples = X_full.shape[0]\n n_features = X_full.shape[1]\n\n # Estimate the score on the entire dataset, with no missing values\n estimator = RandomForestRegressor(random_state=0, n_estimators=100)\n full_scores = cross_val_score(estimator, X_full, y_full,\n scoring='neg_mean_squared_error')\n\n # Add missing values in 75% of the lines\n missing_rate = 0.75\n n_missing_samples = int(np.floor(n_samples * missing_rate))\n missing_samples = np.hstack((np.zeros(n_samples - n_missing_samples,\n dtype=np.bool),\n np.ones(n_missing_samples,\n dtype=np.bool)))\n rng.shuffle(missing_samples)\n missing_features = rng.randint(0, n_features, n_missing_samples)\n\n # Estimate the score after replacing missing values by 0\n X_missing = X_full.copy()\n X_missing[np.where(missing_samples)[0], missing_features] = 0\n y_missing = y_full.copy()\n estimator = RandomForestRegressor(random_state=0, n_estimators=100)\n zero_impute_scores = cross_val_score(estimator, X_missing, y_missing,\n scoring='neg_mean_squared_error')\n\n # Estimate the score after imputation (mean strategy) of the missing values\n X_missing = X_full.copy()\n X_missing[np.where(missing_samples)[0], missing_features] = 0\n y_missing = y_full.copy()\n estimator = Pipeline([(\"imputer\", SimpleImputer(missing_values=0,\n strategy=\"mean\")),\n (\"forest\", RandomForestRegressor(random_state=0,\n n_estimators=100))])\n mean_impute_scores = cross_val_score(estimator, X_missing, y_missing,\n scoring='neg_mean_squared_error')\n\n # Estimate the score after imputation (MICE strategy) of the missing values\n estimator = Pipeline([(\"imputer\", MICEImputer(missing_values=0,\n random_state=0)),\n (\"forest\", RandomForestRegressor(random_state=0,\n n_estimators=100))])\n mice_impute_scores = cross_val_score(estimator, X_missing, y_missing,\n scoring='neg_mean_squared_error')\n\n return ((full_scores.mean(), full_scores.std()),\n (zero_impute_scores.mean(), zero_impute_scores.std()),\n (mean_impute_scores.mean(), mean_impute_scores.std()),\n (mice_impute_scores.mean(), mice_impute_scores.std()))\n\n\nresults_diabetes = np.array(get_results(load_diabetes()))\nmses_diabetes = results_diabetes[:, 0] * -1\nstds_diabetes = results_diabetes[:, 1]\n\nresults_boston = np.array(get_results(load_boston()))\nmses_boston = results_boston[:, 0] * -1\nstds_boston = results_boston[:, 1]\n\nn_bars = len(mses_diabetes)\nxval = np.arange(n_bars)\n\nx_labels = ['Full data',\n 'Zero imputation',\n 'Mean Imputation',\n 'MICE Imputation']\ncolors = ['r', 'g', 'b', 'orange']\n\n# plot diabetes results\nplt.figure(figsize=(12, 6))\nax1 = plt.subplot(121)\nfor j in xval:\n ax1.barh(j, mses_diabetes[j], xerr=stds_diabetes[j],\n color=colors[j], alpha=0.6, align='center')\n\nax1.set_title('Imputation Techniques with Diabetes Data')\nax1.set_xlim(left=np.min(mses_diabetes) * 0.9,\n right=np.max(mses_diabetes) * 1.1)\nax1.set_yticks(xval)\nax1.set_xlabel('MSE')\nax1.invert_yaxis()\nax1.set_yticklabels(x_labels)\n\n# plot boston results\nax2 = plt.subplot(122)\nfor j in xval:\n ax2.barh(j, mses_boston[j], xerr=stds_boston[j],\n color=colors[j], alpha=0.6, align='center')\n\nax2.set_title('Imputation Techniques with Boston Data')\nax2.set_yticks(xval)\nax2.set_xlabel('MSE')\nax2.invert_yaxis()\nax2.set_yticklabels([''] * n_bars)\n\nplt.show()"
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"import numpy as np\nimport matplotlib.pyplot as plt\n\nfrom sklearn.datasets import load_diabetes\nfrom sklearn.datasets import load_boston\nfrom sklearn.ensemble import RandomForestRegressor\nfrom sklearn.pipeline import Pipeline\nfrom sklearn.impute import SimpleImputer, ChainedImputer\nfrom sklearn.model_selection import cross_val_score\n\nrng = np.random.RandomState(0)\n\n\ndef get_results(dataset):\n X_full, y_full = dataset.data, dataset.target\n n_samples = X_full.shape[0]\n n_features = X_full.shape[1]\n\n # Estimate the score on the entire dataset, with no missing values\n estimator = RandomForestRegressor(random_state=0, n_estimators=100)\n full_scores = cross_val_score(estimator, X_full, y_full,\n scoring='neg_mean_squared_error')\n\n # Add missing values in 75% of the lines\n missing_rate = 0.75\n n_missing_samples = int(np.floor(n_samples * missing_rate))\n missing_samples = np.hstack((np.zeros(n_samples - n_missing_samples,\n dtype=np.bool),\n np.ones(n_missing_samples,\n dtype=np.bool)))\n rng.shuffle(missing_samples)\n missing_features = rng.randint(0, n_features, n_missing_samples)\n\n # Estimate the score after replacing missing values by 0\n X_missing = X_full.copy()\n X_missing[np.where(missing_samples)[0], missing_features] = 0\n y_missing = y_full.copy()\n estimator = RandomForestRegressor(random_state=0, n_estimators=100)\n zero_impute_scores = cross_val_score(estimator, X_missing, y_missing,\n scoring='neg_mean_squared_error')\n\n # Estimate the score after imputation (mean strategy) of the missing values\n X_missing = X_full.copy()\n X_missing[np.where(missing_samples)[0], missing_features] = 0\n y_missing = y_full.copy()\n estimator = Pipeline([(\"imputer\", SimpleImputer(missing_values=0,\n strategy=\"mean\")),\n (\"forest\", RandomForestRegressor(random_state=0,\n n_estimators=100))])\n mean_impute_scores = cross_val_score(estimator, X_missing, y_missing,\n scoring='neg_mean_squared_error')\n\n # Estimate the score after chained imputation of the missing values\n estimator = Pipeline([(\"imputer\", ChainedImputer(missing_values=0,\n random_state=0)),\n (\"forest\", RandomForestRegressor(random_state=0,\n n_estimators=100))])\n chained_impute_scores = cross_val_score(estimator, X_missing, y_missing,\n scoring='neg_mean_squared_error')\n\n return ((full_scores.mean(), full_scores.std()),\n (zero_impute_scores.mean(), zero_impute_scores.std()),\n (mean_impute_scores.mean(), mean_impute_scores.std()),\n (chained_impute_scores.mean(), chained_impute_scores.std()))\n\n\nresults_diabetes = np.array(get_results(load_diabetes()))\nmses_diabetes = results_diabetes[:, 0] * -1\nstds_diabetes = results_diabetes[:, 1]\n\nresults_boston = np.array(get_results(load_boston()))\nmses_boston = results_boston[:, 0] * -1\nstds_boston = results_boston[:, 1]\n\nn_bars = len(mses_diabetes)\nxval = np.arange(n_bars)\n\nx_labels = ['Full data',\n 'Zero imputation',\n 'Mean Imputation',\n 'Chained Imputation']\ncolors = ['r', 'g', 'b', 'orange']\n\n# plot diabetes results\nplt.figure(figsize=(12, 6))\nax1 = plt.subplot(121)\nfor j in xval:\n ax1.barh(j, mses_diabetes[j], xerr=stds_diabetes[j],\n color=colors[j], alpha=0.6, align='center')\n\nax1.set_title('Imputation Techniques with Diabetes Data')\nax1.set_xlim(left=np.min(mses_diabetes) * 0.9,\n right=np.max(mses_diabetes) * 1.1)\nax1.set_yticks(xval)\nax1.set_xlabel('MSE')\nax1.invert_yaxis()\nax1.set_yticklabels(x_labels)\n\n# plot boston results\nax2 = plt.subplot(122)\nfor j in xval:\n ax2.barh(j, mses_boston[j], xerr=stds_boston[j],\n color=colors[j], alpha=0.6, align='center')\n\nax2.set_title('Imputation Techniques with Boston Data')\nax2.set_yticks(xval)\nax2.set_xlabel('MSE')\nax2.invert_yaxis()\nax2.set_yticklabels([''] * n_bars)\n\nplt.show()"
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dev/_downloads/plot_missing_values.py

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The median is a more robust estimator for data with high magnitude variables
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which could dominate results (otherwise known as a 'long tail').
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Another option is the MICE imputer. This uses round-robin linear regression,
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treating every variable as an output in turn. The version implemented assumes
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Gaussian (output) variables. If your features are obviously non-Normal,
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consider transforming them to look more Normal so as to improve performance.
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Another option is the ``ChainedImputer``. This uses round-robin linear
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regression, treating every variable as an output in turn. The version
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implemented assumes Gaussian (output) variables. If your features are obviously
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non-Normal, consider transforming them to look more Normal so as to improve
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performance.
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"""
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import numpy as np
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from sklearn.datasets import load_boston
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from sklearn.ensemble import RandomForestRegressor
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from sklearn.pipeline import Pipeline
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from sklearn.impute import SimpleImputer, MICEImputer
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from sklearn.impute import SimpleImputer, ChainedImputer
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from sklearn.model_selection import cross_val_score
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rng = np.random.RandomState(0)
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mean_impute_scores = cross_val_score(estimator, X_missing, y_missing,
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scoring='neg_mean_squared_error')
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# Estimate the score after imputation (MICE strategy) of the missing values
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estimator = Pipeline([("imputer", MICEImputer(missing_values=0,
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random_state=0)),
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# Estimate the score after chained imputation of the missing values
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estimator = Pipeline([("imputer", ChainedImputer(missing_values=0,
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random_state=0)),
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("forest", RandomForestRegressor(random_state=0,
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n_estimators=100))])
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mice_impute_scores = cross_val_score(estimator, X_missing, y_missing,
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scoring='neg_mean_squared_error')
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chained_impute_scores = cross_val_score(estimator, X_missing, y_missing,
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scoring='neg_mean_squared_error')
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return ((full_scores.mean(), full_scores.std()),
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(zero_impute_scores.mean(), zero_impute_scores.std()),
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(mean_impute_scores.mean(), mean_impute_scores.std()),
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(mice_impute_scores.mean(), mice_impute_scores.std()))
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(chained_impute_scores.mean(), chained_impute_scores.std()))
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results_diabetes = np.array(get_results(load_diabetes()))
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x_labels = ['Full data',
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'Zero imputation',
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'Mean Imputation',
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'Chained Imputation']
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colors = ['r', 'g', 'b', 'orange']
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# plot diabetes results

dev/_downloads/scikit-learn-docs.pdf

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dev/_images/iris.png

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