Data Organization and Management

Statistics Toolbox provides two specialized array types—categorical arrays and dataset arrays—that enhance MATLAB standard data types by enabling convenient organi- zation and analysis of statistical data.

Categorical Arrays

Categorical arrays let you organize and process categorical data that takes on values from a finite set of discrete levels or catego- ries. With categorical arrays, you can: Store nominal data using descriptive labels, such as “red,” “green,” and “blue” for an unordered set of colorsStore ordinal data using descriptive labels, such as “cold,” “warm,” and “hot” for an ordered set of temperature measurementsManipulate categorical data using familiar array operations and indexing methods Index into other variables or create subsets of data based upon the category of observationGroup observations of the same category for computing statistics and creating visualizations •• ••• •• • •
Regression analysis to determine the most important ingredients for cement-mixture curing. Stepwise regression capabilities in Statistics Toolbox provide automated procedures for identifying models from several potential explanatory variables.

Descriptive Statistics Statistical Plotting and Interactive Graphics

Descriptive statistics methods enable you to quickly understand and describe potentially large sets of data. Statistics Toolbox includes functions for calculating: Measures of central tendency (measures of location), including average, median, and various meansMeasures of dispersion (measures of spread), including range, variance, standard deviation, and mean or median absolute deviationLinear and rank correlation (partial and full) Results based on data with missing values Percentile and quartile estimates Bootstrap statistics Density estimates (using a kernel-smooth-ing function)These functions help you summarize the values in a data sample with a few highly relevant numbers. Statistics Toolbox includes numerous func-tions that help you represent your data graphically. In addition to the standard set of MATLAB plot types, Statistics Toolbox includes box plots, probability plots, histo- grams and 3-D histograms, control charts, quantile-quantile plots, and several multi- variate plots. It also provides interactive graphics that enhance analysis in areas such as:Nonlinear and polynomial fitting and predictionExploration of distribution functions and distribution fitting and analysisInteractive random number generation Response surface modeling Interactive process experimentation and analysisStepwise regression analysis •••• • • •

Dataset Arrays

Dataset arrays enable convenient organiza- tion and analysis of heterogeneous statistical data and metadata. Dataset arrays have columns that represent different measured variables and rows that represent different observations. With dataset arrays, you can:Collect variables of different data types and sizes in a single arrayUse metadata to describe variables and observations, and to access them by nameView summary statistics and display data in an intuitive tabular formatCreate, manage, and operate on dataset arrays using a variety of supporting methods •• •• ••