I often create character variables (i.e. variables with strings of text as their values) in SAS, and they sometimes don’t render as expected. Here is an example involving the built-in data set SASHELP.CLASS. Here is the code: data c1; set sashelp.class; * define a new character variable to classify someone as tall or […]
Yesterday, all 15 home teams in Major League Baseball won on the same day – the first such occurrence in history. CTV News published an article written by Mike Fitzpatrick from The Associated Press that reported on this event. The article states, “Viewing every game as a 50-50 proposition independent of all others, STATS figured the […]
Yesterday, all 15 home teams in Major League Baseball won on the same day – the first such occurrence in history. CTV News published an article written by Mike Fitzpatrick from The Associated Press that reported on this event. The article states, “Viewing every game as a 50-50 proposition independent of all others, STATS figured the […]
Introduction I recently introduced how to use the count() function in the “plyr” package in R to produce 1-way frequency tables in R. Several commenters provided alternative ways of doing so, and they are all appreciated. Today, I want to extend that tutorial by demonstrating how count() can be used to produce N-way frequency tables […]
Introduction I recently introduced how to use the count() function in the “plyr” package in R to produce 1-way frequency tables in R. Several commenters provided alternative ways of doing so, and they are all appreciated. Today, I want to extend that tutorial by demonstrating how count() can be used to produce N-way frequency tables […]
Introduction One feature that I like about R is the ability to access and manipulate the outputs of many functions. For example, you can extract the kernel density estimates from density() and scale them to ensure that the resulting density integrates to 1 over its support set. I recently needed to get a frequency table of […]
Introduction One feature that I like about R is the ability to access and manipulate the outputs of many functions. For example, you can extract the kernel density estimates from density() and scale them to ensure that the resulting density integrates to 1 over its support set. I recently needed to get a frequency table of […]
Introduction My statistics education focused a lot on normal linear least-squares regression, and I was even told by a professor in an introductory statistics class that 95% of statistical consulting can be done with knowledge learned up to and including a course in linear regression. Unfortunately, that advice has turned out to vastly underestimate the […]
Introduction The chi-squared test of independence is one of the most basic and common hypothesis tests in the statistical analysis of categorical data. Given 2 categorical random variables, and , the chi-squared test of independence determines whether or not there exists a statistical dependence between them. Formally, it is a hypothesis test with the following null and […]
For a binary classifier, its positive predictive value (PPV) is the proportion of positively classified cases that were truly positive. its negative predictive value (NPV) is the proportion of negatively classified cases that were truly negative. In a later Statistics and Machine Learning Lesson of the Day, I will discuss the differences between PPV/NPV and sensitivity/specificity […]
