The DO Loop

Analytics

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

Rick WicklinJanuary 23, 2019 0

Coding and simulating categorical variables in regression models

Recently I was asked to explain the result of an ANOVA analysis that I posted to a statistical discussion forum. My program included some simulated data for an ANOVA model and a call to the GLM procedure to estimate the parameters. I was asked why the parameter estimates from PROC

English

Analytics | Machine Learning | Programming Tips

Partition data into training, validation, and testing in SAS

Rick WicklinJanuary 21, 2019 7

Create training, validation, and test data sets in SAS

In machine learning and other model building techniques, it is common to partition a large data set into three segments: training, validation, and testing. Training data is used to fit each model. Validation data is a random sample that is used for model selection. These data are used to select

English

Analytics | Programming Tips

Rick WicklinJanuary 16, 2019 10

Three ways to add a line to a Q-Q plot

A quantile-quantile plot (Q-Q plot) is a graphical tool that compares a data distribution and a specified probability distribution. If the points in a Q-Q plot appear to fall on a straight line, that is evidence that the data can be approximately modeled by the target distribution. Although it is

English

Analytics | Data Visualization | Programming Tips

Process flow diagram shows how to resample data to create a bootstrap distribution.

Rick WicklinJanuary 9, 2019 0

10 posts from 2018 that deserve a second look

Numbers don't lie, but sometimes they don't reveal the full story. Last week I wrote about the most popular articles from The DO Loop in 2018. The popular articles are inevitably about elementary topics in SAS programming or statistics because those topics have broad appeal. However, I also write about

English

Analytics | Programming Tips

Rick WicklinJanuary 7, 2019 34

Deming regression for comparing different measurement methods

Deming regression (also called errors-in-variables regression) is a total regression method that fits a regression line when the measurements of both the explanatory variable (X) and the response variable (Y) are assumed to be subject to normally distributed errors. Recall that in ordinary least squares regression, the explanatory variable (X)

English

Analytics | Data Visualization

Rick WicklinDecember 19, 2018 15

Visualize a mixed model that has repeated measures or random coefficients

I regularly see questions on a SAS discussion forum about how to visualize the predicted values for a mixed model that has at least one continuous variable, a categorical variable, and possibly an interaction term. SAS procedures such as GLM, GENMOD, and LOGISTIC can automatically produce plots of the predicted

English

Analytics | Data Visualization | Learn SAS

Rick WicklinDecember 17, 2018 0

Create a probability plot in SAS

Many data analysts use a quantile-quantile plot (Q-Q plot) to graphically assess whether data can be modeled by a probability distribution such as the normal, lognormal, or gamma distribution. You can use the QQPLOT statement in PROC UNIVARIATE to create a Q-Q plot for about a dozen common distributions. However,

English

Analytics | Learn SAS | Programming Tips

Rick WicklinDecember 12, 2018 7

The essential guide to bootstrapping in SAS

This article describes best practices and techniques that every data analyst should know before bootstrapping in SAS. The bootstrap method is a powerful statistical technique, but it can be a challenge to implement it efficiently. An inefficient bootstrap program can take hours to run, whereas a well-written program can give

English

Analytics | Data Visualization

Rick WicklinNovember 26, 2018 4

A funnel plot for immunization rates

Last week my colleague, Robert Allison, visualized data regarding immunization rates for kindergarten classes in North Carolina. One of his graphs was a scatter plot that displayed the proportion of unimmunized students versus the size of the class for 1,885 kindergarten classes in NC. This scatter plot is the basis

English

Analytics | Learn SAS

Graph of norm of solutions to the singular system A*b=c. The norm is plotted for vectors b + alpha*x_Null where b is the Moore-Penrose solution and x_Null is a basis for the nullspace of A.

Rick WicklinNovember 21, 2018 2

Generalized inverses for matrices

A data analyst asked how to compute parameter estimates in a linear regression model when the underlying data matrix is rank deficient. This situation can occur if one of the variables in the regression is a linear combination of other variables. It also occurs when you use the GLM parameterization

English

Blogs

Blogs

Analytics