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Rick WicklinApril 2, 2014 0

A different way to interpret the negative binomial distribution

While at SAS Global Forum 2014 I attended a talk by Jorge G. Morel on the analysis of data with overdispersion. (His slides are available, along with a video of his presentation.) The Wikipedia defines overdispersion as "greater variability than expected from a simple model." For count data, the "simple

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Advanced Analytics | Machine Learning

Jared DeanMarch 21, 2014 0

March Madness and Predictive Modeling

In my region of North Carolina (Raleigh, Durham, and Chapel Hill) one of the most anticipated times of the year has arrived— the NCAA basketball tournament. This is a great time of year for me, because I get to combine several of my passions. For those who don’t live among crazed college

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Advanced Analytics

Rick WicklinMarch 19, 2014 0

Define functions with optional parameters in SAS/IML

Last month I blogged about defining SAS/IML functions that have default parameter values. This language feature, which was introduced in SAS/IML 12.1, enables you to skip arguments when you call a user-defined function. The same technique enables you to define optional parameters. Inside the function, you can determine whether the

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Advanced Analytics | Learn SAS

Rick WicklinMarch 17, 2014 0

Finding elements in one vector that are not in another vector

The SAS/IML language has several functions for finding the unions, intersections, and differences between sets. In fact, two of my favorite utility functions are the UNIQUE function, which returns the unique elements in a matrix, and the SETDIF function, which returns the elements that are in one vector and not

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Advanced Analytics

Rick WicklinMarch 14, 2014 0

For pi day: A continued fraction expansion of pi

Many geeky mathematical people celebrate "pi day" on March 14, because the date is written 3/14 in the US, which is evocative of the decimal representation of π = 3.14.... Most people are familiar with the decimal representation of π. The media occasionally reports on a new computational tour-de-force that

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Advanced Analytics

Rick WicklinFebruary 24, 2014 0

Three ways to add a smoothing spline to a scatter plot in SAS

Like many SAS programmers, I use the Statistical Graphics (SG) procedures to graph my data in SAS. To me, the SGPLOT and SGRENDER procedures are powerful, easy to use, and produce fabulous ODS graphics. I was therefore surprised when a SAS customer told me that he continues to use the

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Advanced Analytics | Learn SAS

Rick WicklinFebruary 19, 2014 0

Techniques for scoring a regression model in SAS

My previous post described how to use the "missing response trick" to score a regression model. As I said in that article, there are other ways to score a regression model. This article describes using the SCORE procedure, a SCORE statement, the relatively new PLM procedure, and the CODE statement.

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Advanced Analytics | Learn SAS

Rick WicklinFebruary 17, 2014 0

The missing value trick for scoring a regression model

A fundamental operation in statistical data analysis is to fit a statistical regression model on one set of data and then evaluate the model on another set of data. The act of evaluating the model on the second set of data is called scoring. One of first "tricks" that I

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Advanced Analytics | Data Management | Data Visualization

David PopeFebruary 15, 2014 0

Does the architecture matter as much as the analytics?

I was recently part of team discussing enterprise architecture with a chief IT architect, and we were explaining how SAS can integrate into their existing infrastructure, add business value on top it and even fit into their future planned infrastructure. This conversation was one of the reasons I blogged about

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Advanced Analytics | SAS Events | Students & Educators

Polly Mitchell-GuthrieFebruary 7, 2014 0

Skills needed for competitive advantage in analytics (hint, it's not just the math)

I'm a big believer in both/and thinking, so I'll stand squarely in the middle and say that the most important skills for competitive advantage in analytics include a combination of top-notch modeling abilities along with business acumen, critical thinking, and curiosity. I was intrigued by a blog post on this

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Advanced Analytics

Kenneth SanfordJanuary 28, 2014 0

Using panel data to measure the economic impact of the Super Bowl

This year the Super Bowl will take place in East Rutherford, New Jersey at MetLife Stadium just outside New York City. For the first time in this event’s 48-year history, the game will take place outdoors in a cold-weather environment, potentially subjecting players and fans to sub-freezing temperatures. The fans

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Advanced Analytics

Rick WicklinJanuary 21, 2014 0

The best articles of 2013: Twelve posts from The DO Loop that merit a second look

I began 2014 by compiling a list of 13 popular articles from my blog in 2013. Although this "People's Choice" list contains many articles that I am proud of, it did not include all of my favorites, so I decided to compile an "Editor's Choice" list. The blog posts on

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Advanced Analytics

Rick WicklinJanuary 7, 2014 0

13 popular articles from 2013

In 2013 I published 110 blog posts. Some of these articles were more popular than others, often because they were linked to from a SAS newsletter such as the SAS Statistics and Operations Research News. In no particular order, here are some of my most popular posts from 2013, organized

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Advanced Analytics

Rick WicklinDecember 4, 2013 0

Secret Santa: What is the probability that someone pulls her own name from a hat?

Each year my siblings choose names for a Christmas gift exchange. It is not unusual for a sibling to pick her own name, whereupon the name is replaced into the hat and a new name is drawn. In fact, that "glitch" in the drawing process was a motivation for me

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Advanced Analytics

Gerhard SvolbaDecember 3, 2013 0

"The hungry statistician" – or why we never can get enough data

As the “Year of Statistics” comes to a close, I write this blog in support of the many statisticians who carefully fulfil their analysis tasks day by day, and to defend what may appear to be demanding behavior when it comes to data requirements. How do statisticians get this reputation? Are we

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Advanced Analytics

Rick WicklinNovember 25, 2013 0

Twelve advantages to calling R from the SAS/IML language

For several years, there has been interest in calling R from SAS software, primarily because of the large number of special-purpose R packages. The ability to call R from SAS has been available in SAS/IML since 2009. Previous blog posts about R include a video on how to call R

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Advanced Analytics

Juthika KharghariaNovember 22, 2013 0

How WAVELETS can help separate the signal from the noise

Wavelet analysis is an exciting and relatively new field of study that enables one to extract underlying patterns either from spatially varying or temporally varying data. Pixel values representing the relative brightness and color that constitute an image are an example of spatially varying data, and daily variations of financial

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Advanced Analytics

Rick WicklinNovember 20, 2013 0

Write a reusable SAS/IML module that passes values to R

When I call R from within the SAS/IML language, I often pass parameters from SAS into R. This feature enables me to write general-purpose, reusable, modules that can analyze data from many different data sets. I've previously blogged about how to pass values to SAS procedures from PROC IML by

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Advanced Analytics | SAS Events | Students & Educators

Jerry OglesbyOctober 18, 2013 0

ANALYTICS 2013 – A BEST PRACTICE CONFERENCE FOR ANALYTICS PROFESSIONALS

We are in the final countdown to the Analytics 2013 Conference to be held next week, October 21-22 at the Hyatt Regency Orlando. There is a power-packed agenda for the conference, featuring four very strong keynote presentations from Dr. Jim Goodnight, CEO of SAS; Ed Gaffin, Walt Disney World; Will Hakes,

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Advanced Analytics

Gerhard SvolbaOctober 13, 2013 0

Why my aunt Susanne and her friends give us a hard time in statistical analysis

My aunt Susanne is an elderly lady, who lives at the countryside and looks forward to celebrating her 80th birthday soon. Since the 1960's she has had a telephone connection with her fixed line provider. At that time, and for many years later, in the country where my aunt lives,

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Advanced Analytics | Learn SAS

Rick WicklinSeptember 30, 2013 0

Generate combinations in SAS

Last week I described how to generate permutations in SAS. A related concept is the "combination." In probability and statistics, a combination is a subset of k items chosen from a set that contains N items. Order does not matter, so although the ordered triplets (B, A, C) and (C,

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Advanced Analytics

Patrick MaherSeptember 27, 2013 0

The truth about the big data evolution (or at least as I see it)

Some recent press articles question the value of big data while a book takes the opposite approach; I’ll choose the middle way. The New York Times article ‘Is Big Data an Economic Big Dud?’ questions the value of digital data and the resulting increase in the amount of data. This

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Advanced Analytics

Rick WicklinSeptember 25, 2013 0

Compute contours of the bivariate normal CDF

This is the last post in my recent series of articles on computing contours in SAS. Last month a SAS customer asked how to compute the contours of the bivariate normal cumulative distribution function (CDF). Answering that question in a single blog post would have resulted in a long article,

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Advanced Analytics | Learn SAS

Rick WicklinSeptember 23, 2013 0

Generate permutations in SAS

I've written several articles that show how to generate permutations in SAS. In the SAS DATA step, you can use the ALLPEM subroutine to generate all permutations of a DATA step array that contain a small number (18 or fewer) elements. In addition, the PLAN procedure enables you to generate

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Advanced Analytics

Rick WicklinJuly 26, 2013 0

How to choose parameters so that a distribution has a specified mean and variance

The truncated normal distribution TN(μ, σ, a, b) is the distribution of a normal random variable with mean μ and standard deviation σ that is truncated on the interval [a, b]. I previously blogged about how to implement the truncated normal distribution in SAS. A friend wanted to simulate data

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Advanced Analytics

Juthika KharghariaJuly 12, 2013 0

How incremental response modeling can help you reach the right target group more precisely

Did you know that more than 30,000 Americans die in traffic accidents every year? Interestingly, the U.S. import of mangoes from Brazil is found to be highly correlated with this fatality rate, as shown in the graph below. But are mango imports a good indicator of the future traffic fatality

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Advanced Analytics

Rick WicklinJune 24, 2013 0

Count the number of unique rows in a matrix

How do you count the number of unique rows in a matrix? The simplest algorithm is to sort the data and then iterate down the rows, comparing each row with the previous row. However, this algorithm has two shortcomings: it physically sorts the data (which means that the original locations

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Advanced Analytics

Rick WicklinJune 5, 2013 0

Using simulation to compute a power curve

Last week I showed how to use simulation to estimate the power of a statistical test. I used the two-sample t test to illustrate the technique. In my example, the difference between the means of two groups was 1.2, and the simulation estimated a probability of 0.72 that the t

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Advanced Analytics

Rick WicklinMay 30, 2013 0

Using simulation to estimate the power of a statistical test

The power of a statistical test measures the test's ability to detect a specific alternate hypothesis. For example, educational researchers might want to compare the mean scores of boys and girls on a standardized test. They plan to use the well-known two-sample t test. The null hypothesis is that the

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Advanced Analytics

Rick WicklinApril 29, 2013 0

Understanding local and global variables in the SAS/IML language

The TV show Cheers was set in a bar "where everybody knows your name." Global knowledge of a name is appealing for a neighborhood pub, but not for a programming language. Most programming languages enable you to define functions that have local variables: variables whose names are known only inside

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