Cheat Sheet

Machine Learning For Dummies Cheat Sheet

From Machine Learning For Dummies

By John Paul Mueller, Luca Massaron

Machine learning is an incredible technology that you use more often than you think today and with the potential to do even more tomorrow. The interesting thing about machine learning is that both R and Python make the task easier than more people realize because both languages come with a lot of built-in and extended support (through the use of libraries, datasets, and other resources). With that in mind, this cheat sheet helps you access the most commonly needed reminders for making your machine learning experience fast and easy.

Choosing the Right Algorithm for Machine Learning

Machine learning involves the use of many different algorithms. This table gives you a quick summary of the strengths and weaknesses of various algorithms.

Algorithm Best at Pros Cons
Random Forest Apt at almost any machine learning problem

Can work in parallel

Seldom overfits

Automatically handles missing values

No need to transform any variable

No need to tweak parameters

Can be used by almost anyone with excellent results
Difficult to interpret

Weaker on regression when estimating values at the extremities of the distribution of response values

Biased in multiclass problems toward more frequent classes
Gradient Boosting Apt at almost any machine learning problem

Search engines (solving the problem of learning to rank)
It can approximate most nonlinear function

Best in class predictor

Automatically handles missing values

No need to transform any variable
It can overfit if run for too many iterations

Sensitive to noisy data and outliers

Doesn’t work well without parameter tuning
Linear regression Baseline predictions

Econometric predictions

Modelling marketing responses
Simple to understand and explain

It seldom overfits

Using L1 & L2 regularization is effective in feature selection

Fast to train

Easy to train on big data thanks to its stochastic version
You have to work hard to make it fit nonlinear functions

Can suffer from outliers
Support Vector Machines Character recognition

Image recognition

Text classification
Automatic nonlinear feature creation

Can approximate complex nonlinear functions
Difficult to interpret when applying nonlinear kernels

Suffers from too many examples, after 10,000 examples it starts taking too long to train
K-nearest Neighbors Computer vision

Multilabel tagging

Recommender systems

Spell checking problems
Fast, lazy training

Can naturally handle extreme multiclass problems (like tagging text)
Slow and cumbersome in the predicting phase

Can fail to predict correctly due to the curse of dimensionality
Adaboost Face detection Automatically handles missing values

No need to transform any variable

It doesn’t overfit easily

Few parameters to tweak

It can leverage many different weak-learners
Sensitive to noisy data and outliers

Never the best in class predictions
Naive Bayes Face recognition

Sentiment analysis

Spam detection

Text classification
Easy and fast to implement, doesn’t require too much memory and can be used for online learning

Easy to understand

Takes into account prior knowledge
Strong and unrealistic feature independence assumptions

Fails estimating rare occurrences

Suffers from irrelevant features
Neural Networks Image recognition

Language recognition and translation

Speech recognition

Vision recognition
Can approximate any nonlinear function

Robust to outliers

Works only with a portion of the examples (the support vectors)
Very difficult to set up

Difficult to tune because of too many parameters and you have also to decide the architecture of the network

Difficult to interpret

Easy to overfit
Logistic regression Ordering results by probability

Modelling marketing responses
Simple to understand and explain

It seldom overfits

Using L1 & L2 regularization is effective in feature selection

The best algorithm for predicting probabilities of an event

Fast to train

Easy to train on big data thanks to its stochastic version
You have to work hard to make it fit nonlinear functions

Can suffer from outliers
SVD Recommender systems Can restructure data in a meaningful way Difficult to understand why data has been restructured in a certain way
PCA Removing collinearity

Reducing dimensions of the dataset
Can reduce data dimensionality Implies strong linear assumptions (components are a weighted summations of features)
K-means Segmentation Fast in finding clusters

Can detect outliers in multiple dimensions
Suffers from multicollinearity

Clusters are spherical, can’t detect groups of other shape

Unstable solutions, depends on initialization

Getting the Right Library for Machine Learning

When working with R and Python for machine learning, you gain the benefit of not having to reinvent the wheel when it comes to algorithms. There is a library available to meet your specific needs — you just need to know which one to use. This table provides you with a listing of the libraries used for machine learning for both R and Python. When you want to perform any algorithm-related task, simply load the library needed for that task into your programming environment.

Algorithm Python implementation R implementation
Adaboost sklearn.ensemble.AdaBoostClassifier

library(ada) : ada
Gradient Boosting sklearn.ensemble.GradientBoostingClassifier

library(gbm) : gbm
K-means sklearn.cluster.KMeans

library(stats) : kmeans
K-nearest Neighbors sklearn.neighbors.KNeighborsClassifier

library(class): knn
Linear regression sklearn.linear_model.LinearRegression




library(stats) : lm

library(stats) : glm

library(MASS) : lm.ridge

library(lars) : lars

library(glmnet) : glmnet
Logistic regression sklearn.linear_model.LogisticRegression

library(stats) : glm

library(glmnet) : glmnet
Naive Bayes sklearn.naive_bayes.GaussianNB


library(klaR) : NaiveBayes

library(e1071) : naiveBayes
Neural Networks sklearn.neural_network.BernoulliRBM

(in version 0.18 of Scikit-learn, a new implementation of supervised neural network will be introducted)
library(neuralnet) : neuralnet

library(AMORE) : train

library(nnet) : nnet
PCA sklearn.decomposition.PCA library(stats): princomp

library(stats) : stats
Random Forest sklearn.ensemble.RandomForestClassifier



library(randomForest) : randomForest
Support Vector Machines sklearn.svm.SVC






library(e1071) : svm
SVD sklearn.decomposition.TruncatedSVD

library(irlba) : irlba

library(svd) : svd

Locating the Algorithm You Need for Machine Learning

There are a number of different algorithms you can use for machine learning. However, finding the specific algorithm you want to know about can be difficult. This table provides you with the online location for information about the algorithms used in machine learning.

Algorithm Type Python/R URL
Naive Bayes Supervised classification, online learning
PCA Unsupervised
SVD Unsupervised
K-means Unsupervised
K-nearest Neighbors Supervised regression and classification
Linear Regression Supervised regression, online learning
Logistic Regression Supervised classification, online learning
Neural Networks Unsupervised Supervised regression and classification
Support Vector Machines Supervised regression and classification
Adaboost Supervised classification
Gradient Boosting Supervised regression and classification
Random Forest Supervised regression and classification