# Improve Training Time of Machine Learning Model Using Bagging | KGP Talkie

## How bagging works

First of all we will try to understand what `Bagging`

is from the following diagram:

Let's say we have a dataset to train the model, first we need to divide this dataset into `number of datasets(atleast more than 2)`

.And then we need to apply ``classifier`

on each of the dataset seperately then finally we do aggregation`to get the`

output`.

SVM time complexity = *O*(*n*3)

i.e. As we increase number of input samples, training time increases cubically.

##### For Example

if `1000 input samples`

take `10 seconds`

to train then `3000 input samples`

might take `10 * 3^3 seconds`

to train.

If we divide `3000`

samples into `3`

categories each dataset contain `1000`

samples. To train each dataset it will take `10sec`

in this way it will get over all time to train is `30sec(10+10+10)`

. In this way we can improve `training time`

of machine learning model.

Instead of 270sec, if we divide into 3 sets it will take 30sec.

Let's have a look into the following script:

Importing required libraries

import numpy as np from sklearn.ensemble import BaggingClassifier from sklearn import datasets from sklearn.svm import SVC

Importing iris dataset

iris = datasets.load_iris() iris.keys()

dict_keys(['data', 'target', 'target_names', 'DESCR', 'feature_names', 'filename'])

Let's see the description of the iris dataset

print(iris.DESCR)

.. _iris_dataset: Iris plants dataset -------------------- **Data Set Characteristics:** :Number of Instances: 150 (50 in each of three classes) :Number of Attributes: 4 numeric, predictive attributes and the class :Attribute Information: - sepal length in cm - sepal width in cm - petal length in cm - petal width in cm - class: - Iris-Setosa - Iris-Versicolour - Iris-Virginica :Summary Statistics: ============== ==== ==== ======= ===== ==================== Min Max Mean SD Class Correlation ============== ==== ==== ======= ===== ==================== sepal length: 4.3 7.9 5.84 0.83 0.7826 sepal width: 2.0 4.4 3.05 0.43 -0.4194 petal length: 1.0 6.9 3.76 1.76 0.9490 (high!) petal width: 0.1 2.5 1.20 0.76 0.9565 (high!) ============== ==== ==== ======= ===== ==================== :Missing Attribute Values: None :Class Distribution: 33.3% for each of 3 classes. :Creator: R.A. Fisher :Donor: Michael Marshall (MARSHALL%PLU@io.arc.nasa.gov) :Date: July, 1988 The famous Iris database, first used by Sir R.A. Fisher. The dataset is taken from Fisher's paper. Note that it's the same as in R, but not as in the UCI Machine Learning Repository, which has two wrong data points. This is perhaps the best known database to be found in the pattern recognition literature. Fisher's paper is a classic in the field and is referenced frequently to this day. (See Duda & Hart, for example.) The data set contains 3 classes of 50 instances each, where each class refers to a type of iris plant. One class is linearly separable from the other 2; the latter are NOT linearly separable from each other.

X = iris.data y = iris.target

Let's go ahead and get the shape of these x and y

X.shape, y.shape

((150, 4), (150,))

So x has `150`

samples and `4`

attributes . y has `150`

samples.

We know 150 samples are less number of samples in machine leaning.So to get more number of samples we will use repeat() function .

We will repeat these `150`

samples to `500`

times then we will get 7`5000`

samples.

X = np.repeat(X, repeats=500, axis = 0) y = np.repeat(y, repeats=500, axis = 0)

X.shape, y.shape

((75000, 4), (75000,))

### Train without `Bagging`

Now to train the model without bagging we will create a classifier called `SVC()`

with `linear`

kernel.

%%time clf = SVC(kernel='linear', probability=True, class_weight='balanced') clf.fit(X, y) print('SVC: ', clf.score(X, y))

SVC: 0.98 Wall time: 34.5sec

### Train it with `Bagging`

Now to train the model with bagging we will create a classifier called `BaggingClassifier()`

with `linear`

kernel.

%%time n_estimators = 10 clf = BaggingClassifier(SVC(kernel='linear', probability=True, class_weight='balanced'), n_estimators=n_estimators, max_samples=1.0/n_estimators) clf.fit(X, y) print('SVC: ', clf.score(X, y))

SVC: 0.98 Wall time: 10.5 s

So from the above result we can observe improvement training time of the model from `34.5sec`

to `10.5sec`

.

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