Learning to Classify with Branching Tests: "A decision tree takes as input an object or situation described by a set of properties, and outputs a yes/no decision. Decision trees therefore represent Boolean functions. Functions with a larger range of outputs can also be represented...."
– Artificial Intelligence: A Modern Approach. By Stuart Russell & Peter Norvig. 2002. Section 18.3; page 531.
Once, on a crisp cloudless morning in early fall, a machine learning engineer left her home to seek the answers that she could not find, even in the newly-optimized Google results. She closed her laptop, put on her backpack and hiking boots, and walked quietly out her door and past her mailbox, down a dusty path that led past a stream, until the houses around her gave way to broad fields full of ripening corn. She walked past farms where cows grazed peacefully underneath enormous data silos, until the rows of crops gave way to a smattering of graceful pines and oaks, and she found herself in a forest clearing, headed into the woods. She went deeper through the decision trees and finally stopped near a data stream around midday to have lunch and stretch her legs. The sun made its way through the sky and eventually, she walked further, out of the forest.
Ensemble Learning is taking the predictions of multiple models and assume the output to be having the most votes. When you train multiple Decision Trees each on some random sampling of the dataset and for predictions you take predictions of all the trees, the output class would be the class which gets the most votes. This approach is called Random Forest. Voting classifier is when you train the data on multiple classifier such as Logistic Regression, SVM, RF and other classifiers and the majority vote is the predicted output class ie hard classifier. Voting can also be taken as soft by taking argmax of the outputs.
As a lifelong computational scientist (and now data scientist) I have always been fascinated with numbers, especially lists and tables of things ( databases!). For example, I thought early in life that I wanted to be a Math major in college and study number theory so that I could learn all of the amazing ways to do cool stuff with numbers. But I also wanted to study the wonders of the Universe as an astronomer, so I went on to get a PhD in astrophysics! That career path allowed me to study and apply all of the disciplines that I enjoy: math, physics, astronomy, computational modeling, and data science! It was numbers all the time!
Till now we have learned about linear regression, logistic regression, and they were pretty hard to understand. Let's now start with Decision tree's and I assure you this is probably the easiest algorithm in Machine Learning. There's not much mathematics involved here. Since it is very easy to use and interpret it is one of the most widely used and practical methods used in Machine Learning. Root Nodes – It is the node present at the beginning of a decision tree from this node the population starts dividing according to various features.
As Artificial Intelligence (AI) is used in more applications, the need to consider and mitigate biases from the learned models has followed. Most works in developing fair learning algorithms focus on the offline setting. However, in many real-world applications data comes in an online fashion and needs to be processed on the fly. Moreover, in practical application, there is a trade-off between accuracy and fairness that needs to be accounted for, but current methods often have multiple hyperparameters with non-trivial interaction to achieve fairness. In this paper, we propose a flexible ensemble algorithm for fair decision-making in the more challenging context of evolving online settings. This algorithm, called FARF (Fair and Adaptive Random Forests), is based on using online component classifiers and updating them according to the current distribution, that also accounts for fairness and a single hyperparameters that alters fairness-accuracy balance. Experiments on real-world discriminated data streams demonstrate the utility of FARF.
Gradient Boosting algorithms tackle one of the biggest problems in Machine Learning: bias. Decision Trees is a simple and flexible algorithm. An underfit Decision Tree has low depth, meaning it splits the dataset only a few of times in an attempt to separate the data. Because it doesn't separate the dataset into more and more distinct observations, it can't capture the true patterns in it. When it comes to tree-based algorithms Random Forests was revolutionary, because it used Bagging to reduce the overall variance of the model with an ensemble of random trees.
We have entered a new era of machine learning (ML), where the most accurate algorithm with superior predictive power may not even be deployable, unless it is admissible under the regulatory constraints. This has led to great interest in developing fair, transparent and trustworthy ML methods. The purpose of this article is to introduce a new information-theoretic learning framework (admissible machine learning) and algorithmic risk-management tools (InfoGram, L-features, ALFA-testing) that can guide an analyst to redesign off-the-shelf ML methods to be regulatory compliant, while maintaining good prediction accuracy. We have illustrated our approach using several real-data examples from financial sectors, biomedical research, marketing campaigns, and the criminal justice system.