Statistical Learning
R vs Python? No! R and Python (and something else)
Before assessing R and Python, I will start with Wolfram Mathematica. You can handle lists and matrices easily, you have all the best mathematical functions, backup of Wolfram Alpha and extremely sophisticated graphics visualizations, that allow you, for instance, to make and visualize an animated gradient descent, animate different weights for a given neural network, choose a specific Machine Learning algorithm and automatically classify your dataset in classes, plot stunning 3D visualizations, make animations and manipulate variables values dynamically at the same time you see the output of your calculation. It has 4.65 Gb size and comes with all libraries integrated. It's a great program when you know the formulae for Machine Learning algorithms, so you can build them from scratch, in a completely customized way. You can also do face recognition, geolocation of objects with 3D plots of map surface, handle cellular automata like any other and develop social networks models with artificial intelligence completely customized.
dmlc/xgboost
This plugin currently works with the CLI version and python version. The maximum number of nodes needed for a given tree depth d is 2d 1 - 1. The maximum number of nodes on any given level is 2d. Data is stored in a sparse format. For example, missing values produced by one hot encoding are not stored.
Inferring object rankings based on noisy pairwise comparisons from multiple annotators
Gupta, Rahul, Narayanan, Shrikanth
Ranking a set of objects involves establishing an order allowing for comparisons between any pair of objects in the set. Oftentimes, due to the unavailability of a ground truth of ranked orders, researchers resort to obtaining judgments from multiple annotators followed by inferring the ground truth based on the collective knowledge of the crowd. However, the aggregation is often ad-hoc and involves imposing stringent assumptions in inferring the ground truth (e.g. majority vote). In this work, we propose Expectation-Maximization (EM) based algorithms that rely on the judgments from multiple annotators and the object attributes for inferring the latent ground truth. The algorithm learns the relation between the latent ground truth and object attributes as well as annotator specific probabilities of flipping, a metric to assess annotator quality. We further extend the EM algorithm to allow for a variable probability of flipping based on the pair of objects at hand. We test our algorithms on two data sets with synthetic annotations and investigate the impact of annotator quality and quantity on the inferred ground truth. We also obtain the results on two other data sets with annotations from machine/human annotators and interpret the output trends based on the data characteristics.
Parsimonious Online Learning with Kernels via Sparse Projections in Function Space
Koppel, Alec, Warnell, Garrett, Stump, Ethan, Ribeiro, Alejandro
Despite their attractiveness, popular perception is that techniques for nonparametric function approximation do not scale to streaming data due to an intractable growth in the amount of storage they require. To solve this problem in a memory-affordable way, we propose an online technique based on functional stochastic gradient descent in tandem with supervised sparsification based on greedy function subspace projections. The method, called parsimonious online learning with kernels (POLK), provides a controllable tradeoff? between its solution accuracy and the amount of memory it requires. We derive conditions under which the generated function sequence converges almost surely to the optimal function, and we establish that the memory requirement remains finite. We evaluate POLK for kernel multi-class logistic regression and kernel hinge-loss classification on three canonical data sets: a synthetic Gaussian mixture model, the MNIST hand-written digits, and the Brodatz texture database. On all three tasks, we observe a favorable tradeoff of objective function evaluation, classification performance, and complexity of the nonparametric regressor extracted the proposed method.
Fast Stability Scanning for Future Grid Scenario Analysis
Liu, Ruidong, Verbic, Gregor, Ma, Jin
Future grid scenario analysis requires a major departure from conventional power system planning, where only a handful of most critical conditions is typically analyzed. To capture the inter-seasonal variations in renewable generation of a future grid scenario necessitates the use of computationally intensive time-series analysis. In this paper, we propose a planning framework for fast stability scanning of future grid scenarios using a novel feature selection algorithm and a novel self-adaptive PSO-k-means clustering algorithm. To achieve the computational speed-up, the stability analysis is performed only on small number of representative cluster centroids instead of on the full set of operating conditions. As a case study, we perform small-signal stability and steady-state voltage stability scanning of a simplified model of the Australian National Electricity Market with significant penetration of renewable generation. The simulation results show the effectiveness of the proposed approach. Compared to an exhaustive time series scanning, the proposed framework reduced the computational burden up to ten times, with an acceptable level of accuracy.
Book: Mastering Python for Data Science
If you are a Python developer who wants to master the world of data science then this book is for you. Some knowledge of data science is assumed. Derive inferences from the analysis by performing inferential statistics Evaluate and apply the linear regression technique to estimate the relationships among variables. Evaluate and apply the linear regression technique to estimate the relationships among variables. Evaluate and apply the linear regression technique to estimate the relationships among variables.
Large Scale Decision Forests: Lessons Learned - Sift Science Engineering Blog
We at Sift Science provide fraud detection for hundreds of customers spanning many industries and use cases. To do this, we have devised a specialized modeling stack that is able to adapt to individual customers while simultaneously delivering a great out-of-box experience for new customers, achieved by mixing the output from a "global" model โ trained on our entire network of data โ with the output from a customer's individualized model. Prior to decision forests, we used a custom-built logistic regression classifier combined with highly specialized feature engineering for our global model. While logistic regression has many great attributes, it is fundamentally limited by its inability to model non-linear interactions between features. At Sift, we tend to think of our modeling stack primarily as an enabler of our feature engineering; more powerful modeling allows us to extract the most insight from our features and can even lead to new classes of features. So when in early 2015 we stopped seeing benefits from feature engineering work, it was clear to us that we needed a major upgrade to our modeling stack.
Cluster Analysis and Unsupervised Machine Learning in Python
Cluster analysis is a staple of unsupervised machine learning and data science. It is very useful for data mining and big data because it automatically finds patterns in the data, without the need for labels, unlike supervised machine learning. In a real-world environment, you can imagine that a robot or an artificial intelligence won't always have access to the optimal answer, or maybe there isn't an optimal correct answer. You'd want that robot to be able to explore the world on its own, and learn things just by looking for patterns. Do you ever wonder how we get the data that we use in our supervised machine learning algorithms?
How to Normalize and Standardize Time Series Data in Python - Machine Learning Mastery
In this tutorial, you discovered how to normalize and standardize time series data in Python. That some machine learning algorithms perform better or even require rescaled data when modeling. How to manually calculate the parameters required for normalization and standardization. How to normalize and standardize time series data using scikit-learn in Python. That some machine learning algorithms perform better or even require rescaled data when modeling. How to manually calculate the parameters required for normalization and standardization. How to normalize and standardize time series data using scikit-learn in Python. Do you have any questions about rescaling time series data or about this post? Ask your questions in the comments and I will do my best to answer.