ML | Feature Scaling – Part 2
Feature Scaling is a technique to standardize the independent features present in the data in a fixed range. It is performed during the data pre-processing to handle highly varying magnitudes or values or units. If feature scaling is not done, then a machine learning algorithm tends to weigh greater values, higher and consider smaller values as the lower values, regardless of the unit of the values.
Example: If an algorithm is not using the feature scaling method then it can consider the value 3000 meters to be greater than 5 km but that’s actually not true and in this case, the algorithm will give wrong predictions. So, we use Feature Scaling to bring all values to the same magnitudes and thus, tackle this issue.
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Techniques to perform Feature Scaling
Consider the two most important ones:
- Min-Max Normalization: This technique re-scales a feature or observation value with distribution value between 0 and 1.
- Standardization: It is a very effective technique which re-scales a feature value so that it has distribution with 0 mean value and variance equals to 1.
Download the dataset:
Go to the link and download Data_for_Feature_Scaling.csv
Code: Python code explaining the working of Feature Scaling on the data
# Python code explaining How to# perform Feature Scaling """ PART 1 Importing Libraries """ import numpy as npimport matplotlib.pyplot as pltimport pandas as pd # Sklearn library from sklearn import preprocessing """ PART 2 Importing Data """ data_set = pd.read_csv('C:\\Users\\dell\\Desktop\\Data_for_Feature_Scaling.csv')data_set.head() # here Features - Age and Salary columns # are taken using slicing# to handle values with varying magnitudex = data_set.iloc[:, 1:3].valuesprint ("\nOriginal data values : \n", x) """ PART 4 Handling the missing values """ from sklearn import preprocessing """ MIN MAX SCALER """ min_max_scaler = preprocessing.MinMaxScaler(feature_range =(0, 1)) # Scaled featurex_after_min_max_scaler = min_max_scaler.fit_transform(x) print ("\nAfter min max Scaling : \n", x_after_min_max_scaler) """ Standardisation """ Standardisation = preprocessing.StandardScaler() # Scaled featurex_after_Standardisation = Standardisation.fit_transform(x) print ("\nAfter Standardisation : \n", x_after_Standardisation) |
Output :
Country Age Salary Purchased 0 France 44 72000 0 1 Spain 27 48000 1 2 Germany 30 54000 0 3 Spain 38 61000 0 4 Germany 40 1000 1 Original data values : [[ 44 72000] [ 27 48000] [ 30 54000] [ 38 61000] [ 40 1000] [ 35 58000] [ 78 52000] [ 48 79000] [ 50 83000] [ 37 67000]] After min max Scaling : [[ 0.33333333 0.86585366] [ 0. 0.57317073] [ 0.05882353 0.64634146] [ 0.21568627 0.73170732] [ 0.25490196 0. ] [ 0.15686275 0.69512195] [ 1. 0.62195122] [ 0.41176471 0.95121951] [ 0.45098039 1. ] [ 0.19607843 0.80487805]] After Standardisation : [[ 0.09536935 0.66527061] [-1.15176827 -0.43586695] [-0.93168516 -0.16058256] [-0.34479687 0.16058256] [-0.1980748 -2.59226136] [-0.56487998 0.02294037] [ 2.58964459 -0.25234403] [ 0.38881349 0.98643574] [ 0.53553557 1.16995867] [-0.41815791 0.43586695]]
