Skip to main content

What is Logistic regression

Logistic Regression Algorithm

Concept of Logistic Regression

A machine learning approach called logistic regression is used to model the likelihood of a binary outcome based on one or more independent factors. The goal of logistic regression is to find the best-fitting logistic function that maps the input variables to a probability output between 0 and 1.

The logistic function, also known as the sigmoid function, takes the form of:

 sigmoid(z) = 1 / (1 + e^-z)

 where z is a linear combination of the input variables and their coefficients.

For example, let's say we have a dataset of customer information, including their age and whether they have purchased a product. We can use logistic regression to predict the probability of a customer making a purchase based on their age.

Binary outcome based on one or more independent factors of logistic regression

Logistic Regression Algorithm:

  • Define the problem and collect data.
  • Choose a hypothesis class (e.g., logistic regression).
  • Define a cost function to measure the difference between predicted and actual values.
  • Optimize the cost function to find the optimal parameters that minimize the cost.
  • Evaluate the model on a test dataset to estimate its performance.

Here's an example code in Python for logistic regression:

python code

# Import libraries

import pandas as pd

import numpy as np

import matplotlib.pyplot as plt

from sklearn.linear_model import LogisticRegression

from sklearn.model_selection import train_test_split

from sklearn.metrics import confusion_matrix

# Load the dataset

data = pd.read_csv('customer_data.CSV)

# Create X and y arrays

X = data['Age'].values.reshape(-1, 1)

y = data['Purchased'].values

# Split the data into training and testing sets

X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=0)

# Create the logistic regression model

model = LogisticRegression()

# Fit the model to the training data

model.fit(X_train, y_train)

# Predict the test set results

y_pred = model.predict(X_test)

# Create a confusion matrix to evaluate the model

cm = confusion_matrix(y_test, y_pred)

print(cm)

# Plot the logistic function

plt.plot(X, model.predict_proba(X)[:,1], color='blue')

plt.scatter(X, y, color='red')

plt.label('Age')

plt.label('Purchased')

plt.show()

In this example, we first load the dataset from a CSV file that contains two columns: "Age" and "Purchased". We then create the X and y arrays by selecting the "Age" and "Purchased" columns, respectively. We reshape the X array to be a column vector so that it can be used with the LogisticRegression model.

We split the data into training and testing sets using the train_test_split() function. We create an instance of the LogisticRegression class and fit the model to the training data using the fit() method.

We then use the predict() method to predict the test set results and create a confusion matrix to evaluate the model's performance. The confusion matrix displays the number of true positives, true negatives, false positives, and false negatives.

Finally, we plot the logistic function and the data points to visualize the relationship between age and the probability of a customer making a purchase.

This is a simple example of logistic regression, but the same principles can be applied to more complex datasets with multiple independent variables.

More complex datasets with multiple independent variables in  logistic regression

Logistic Regression Benefits, Advantages and Disadvantages

Logistic Regression Benefits: 

  • capable of handling independent variables that are both continuous and categorical
  • gives the likelihood that the outcome variable will fall under a specific group.
  • Can be used to understand the relationship between independent and dependent variables

 Logistic Regression Advantages: 

  • Can handle nonlinear relationships between variables
  • Easy to interpret
  • Can handle interaction effects between variables

Logistic Regression Disadvantages: 

  • assumes that the independent and dependent variables have a linear relationship.
  • Can be affected by multicollinearity
  • May overfit the data if the number of independent variables is too large relative to the sample size

Main Contents (TOPICS of Machine Learning Algorithms) 

                                                              CONTINUE TO (Random Forests algorithm)

Comments

Popular posts from this blog

Learn Machine Learning Algorithms

Machine Learning Algorithms with Python Code Contents of Algorithms  1.  ML Linear regression A statistical analysis technique known as "linear regression" is used to simulate the relationship between a dependent variable and one or more independent variables. 2.  ML Logistic regression  Logistic regression: A statistical method used to analyse a dataset in which there are one or more independent variables that determine an outcome. It is used to model the probability of a certain outcome, typically binary (yes/no). 3.  ML Decision trees Decision trees: A machine learning technique that uses a tree-like model of decisions and their possible consequences. It is used for classification and regression analysis, where the goal is to predict the value of a dependent variable based on the values of several independent variables. 4.  ML Random forests Random forests: A machine learning technique that uses multiple decision trees to improve the accuracy of predicti...

What is Naive Bayes algorithm

Naive Bayes Algorithm with Python Concepts of Naive Bayes Naive Bayes is a classification algorithm based on Bayes' theorem, which states that the probability of a hypothesis is updated by considering new evidence. Since it presumes that all features are independent of one another, which may not always be the case in real-world datasets, it is known as a "naive". Despite this limitation, Naive Bayes is widely used in text classification, spam filtering, and sentiment analysis. Naive Bayes Algorithm Define the problem and collect data. Choose a hypothesis class (e.g., Naive Bayes). Compute the prior probability and likelihood of each class based on the training data. Use Bayes' theorem to compute the posterior probability of each class given the input features. Classify the input by choosing the class with the highest posterior probability. Evaluate the model on a test dataset to estimate its performance. Here's an example code in Python for Naive Bayes: Python cod...

What is Linear regression

Linear regression A lgorithm Concept of Linear regression In order to model the relationship between a dependent variable and one or more independent variables, linear regression is a machine learning algorithm. The goal of linear regression is to find a linear equation that best describes the relationship between the variables. Using the values of the independent variables as a starting point, this equation can then be used to predict the value of the dependent variable. There is simply one independent variable and one dependent variable in basic linear regression. The linear equation takes the form of y = mx + b, where y is the dependent variable, x is the independent variable, m is the slope of the line, and b is the y-intercept. For example, let's say we have a dataset of the number of hours studied and the corresponding test scores of a group of students. We can use linear regression to find the relationship between the two variables and predict a student's test scor...

What is Random Forests

Random Forests Algorithm Concepts of Random forests Random forests are an ensemble learning method that combines multiple decision trees to create a more accurate and robust model. In a random forest, multiple decision trees are trained on random subsets of the data and features, and the final prediction is made by averaging the predictions of the individual trees. For example, let's say we have a dataset of customer information, including age, income, education level, and purchase history. We can use a random forest to predict whether a customer will make a purchase based on these attributes. Random forests  Algorithm Define the problem and collect data. Choose a hypothesis class (e.g., random forests). Split the data into training and validation sets. Construct multiple decision trees using random subsets of the data and features. Aggregate the predictions from all the trees to make a final prediction. Evaluate the model on the validation set to estimate its performance. Apply th...