Data Science

by John D. Kelleher

Gauss, in his search for the missing dwarf planet Ceres, developed the method of least squares, which enables us to find the best model that fits a data set such that the error in the fit minimizes the sum of squared differences between the data points in the data set and the model. The method of least squares provided the foundation for statistical learning methods such as linear regression and logistic regression as well as the development of artificial neural network models in artificial intelligence (we will return to least squares, regression analysis, and neural networks in chapter 4). Between 1780 and 1820, around the same time that Laplace and Gauss were making their contributions to statistical learning, a Scottish engineer named William Playfair was inventing statistical graphics and laying the foundations for modern data visualization and exploratory data analysis. Playfair invented the line chart and area chart for time-series data, the bar chart to illustrate comparisons between quantities of different categories, and the pie chart to illustrate proportions within a set.