The DO Loop

Analytics

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

Analytics | Learn SAS | Programming Tips

Rick WicklinSeptember 13, 2021 8

The partition problem

The partition problem has many variations, but recently I encountered it as an interactive puzzle on a computer. (Try a similar game yourself!) The player is presented with an old-fashioned pan-balance scale and a set of objects of different weights. The challenge is to divide (or partition) the objects into

English

Analytics | Data Visualization | Learn SAS

Rick WicklinSeptember 9, 2021 0

Simulate proportions for groups

A statistical programmer asked how to simulate event-trials data for groups. The subjects in each group have a different probability of experiencing the event. This article describes one way to simulate this scenario. The simulation is similar to simulating from a mixture distribution. This article also shows three different ways

English

Analytics | Programming Tips

Rick WicklinSeptember 1, 2021 1

On the number of bootstrap samples

The number of possible bootstrap samples for a sample of size N is big. Really big. Recall that the bootstrap method is a powerful way to analyze the variation in a statistic. To implement the standard bootstrap method, you generate B random bootstrap samples. A bootstrap sample is a sample

English

Analytics | Programming Tips

Rick WicklinAugust 30, 2021 0

Bootstrap correlation coefficients in SAS

You can use the bootstrap method to estimate confidence intervals. Unlike formulas, which assume that the data are drawn from a specified distribution (usually the normal distribution), the bootstrap method does not assume a distribution for the data. There are many articles about how to use SAS to bootstrap statistics

English

Analytics | Data Visualization | Programming Tips

Rick WicklinAugust 23, 2021 1

Sliced survival graphs in SAS

This article shows how to create a "sliced survival plot" for proportional-hazards models that are created by using PROC PHREG in SAS. Graphing the result of a statistical regression model is a valuable way to communicate the predictions of the model. Many SAS procedures use ODS graphics to produce graphs

English

Analytics

Rick WicklinAugust 16, 2021 3

Rankings and the geometry of weighted averages

People love rankings. You've probably seen articles about the best places to live, the best colleges to attend, the best pizza to order, and so on. Each of these is an example of a ranking that is based on multiple characteristics. For example, a list of the best places to

English

Analytics | Data Visualization | Programming Tips

Rick WicklinJuly 19, 2021 1

Copulas and multivariate distributions with normal marginals

After my recent articles on simulating data by using copulas, many readers commented about the power of copulas. Yes, they are powerful, and the geometry of copulas is beautiful. However, it is important to be aware of the limitations of copulas. This article creates a bizarre example of bivariate data,

English

Analytics | Programming Tips

Rick WicklinJuly 14, 2021 0

Compare computational methods for least squares regression

In a previous article, I discussed various ways to solve a least-square linear regression model. I discussed the SWEEP operator (used by many SAS regression routines), the LU-based methods (SOLVE and INV in SAS/IML), and the QR decomposition (CALL QR in SAS/IML). Each method computes the estimates for the regression

English

Analytics | Learn SAS

Rick WicklinJuly 12, 2021 1

The QR algorithm for least-squares regression

In computational statistics, there are often several ways to solve the same problem. For example, there are many ways to solve for the least-squares solution of a linear regression model. A SAS programmer recently mentioned that some open-source software uses the QR algorithm to solve least-squares regression problems and asked

English

Analytics | Programming Tips

Rick WicklinJuly 7, 2021 10

Simulate multivariate correlated data by using PROC COPULA in SAS

In general, it is hard to simulate multivariate data that has a specified correlation structure. Copulas make that task easier for continuous distributions. A previous article presented the geometry behind a copula and explained copulas in an intuitive way. Although I strongly believe that statistical practitioners should be familiar with

English

Blogs

Blogs

Analytics