The DO Loop

Analytics

Find out how analytics, from data mining to cognitive computing, is changing the way we do business

Analytics | Data Visualization | Programming Tips

Rick WicklinNovember 16, 2022 3

A profile plot is a way to display multivariate values for many subjects. The optimal linear profile plot was introduced by John Hartigan in his book Clustering Algorithms (1975). In Michael Friendly's book (SAS System for Statistical Graphics, 1991), Friendly shows how to construct an optimal linear profile by using

English

Analytics | Data Visualization | Learn SAS | Programming Tips

Rick WicklinNovember 7, 2022 0

The area of the convex hull of random points

I recently blogged about how to compute the area of the convex hull of a set of planar points. This article discusses the expected value of the area of the convex hull for n random uniform points in the unit square. The article introduces an exact formula (due to Buchta,

English

Analytics | Learn SAS | Programming Tips

Rick WicklinNovember 2, 2022 0

The area and perimeter of a convex hull

The area of a convex hull enables you to estimate the area of a compact region from a set of discrete observations. For example, a biologist might have multiple sightings of a wolf pack and want to use the convex hull to estimate the area of the wolves' territory. A

English

Analytics | Data Visualization | Learn SAS

Rick WicklinOctober 26, 2022 2

Visualize dependencies of missing values

A SAS programmer asked how to create a graph that shows whether missing values in one variable are associated with certain values of another variable. For example, a patient who is supposed to monitor his blood glucose daily might have more missing measurements near holidays and in the summer months

English

Analytics | Learn SAS | Programming Tips

Rick WicklinOctober 24, 2022 3

Implement binary logistic regression from first principles

I recently gave a presentation about the SAS/IML matrix language in which I emphasized that a matrix language enables you to write complex analyses by using only a few lines of code. In the presentation, I used least squares regression as an example. One participant asked how many additional lines

English

Analytics | Learn SAS | Programming Tips

Rick WicklinOctober 19, 2022 0

On solving rank-deficient systems of equations in SAS

Recently, I needed to write a program that can provide a solution to a regression-type problem, even when the data are degenerate. Mathematically, the problem is an overdetermined linear system of equations X*b = y, where X is an n x p design matrix and y is an n x 1 vector. For most

English

Analytics | Learn SAS

Rick WicklinOctober 12, 2022 0

Reduced regression models and tests for linear hypotheses

On a SAS discussion forum, a statistical programmer asked about how to understand the statistics that are displayed when you use the TEST statement in PROC REG (or other SAS regression procedures) to test for linear relationships between regression coefficients. The documentation for the TEST statement in PROC REG explains

English

Analytics | Learn SAS | Programming Tips

Rick WicklinOctober 3, 2022 1

Compute moments of probability distributions in SAS

A previous article discusses the definitions of three kinds of moments for a continuous probability distribution: raw moments, central moments, and standardized moments. These are defined in terms of integrals over the support of the distribution. Moments are connected to the familiar shape features of a distribution: the mean, variance,

English

Analytics

Rick WicklinSeptember 28, 2022 2

Definitions of moments in probability and statistics

The moments of a continuous probability distribution are often used to describe the shape of the probability density function (PDF). The first four moments (if they exist) are well known because they correspond to familiar descriptive statistics: The first raw moment is the mean of a distribution. For a random

English

Analytics | Learn SAS

Rick WicklinSeptember 21, 2022 1

The noncentral t distribution in SAS

The noncentral t distribution is a probability distribution that is used in power analysis and hypothesis testing. The distribution generalizes the Student t distribution by adding a noncentrality parameter, δ. When δ=0, the noncentral t distribution is the usual (central) t distribution, which is a symmetric distribution. When δ >

English

Blogs

Blogs

Analytics