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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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Rick WicklinFebruary 10, 2014 0

Define functions with default parameter values in SAS/IML

One of my favorite new features of SAS/IML 12.1 enables you to define functions that contain default values for parameters. This is extremely useful when you want to write a function that has optional arguments. Example: Centering a data vector It is simple to specify a SAS/IML module with a

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Shelly GoodinJanuary 24, 2014 0

SAS author's tip: Planning versus forecasting and manual overrides

This week's SAS tip is from Applied Data Mining for Forecasting Using SAS by Tim Rey, Arthur Kordon, and Chip Wells. Whether you're a forecasting practitioner, engineer, statistician, or economist, you'll appreciate the many real-world examples in the book. And hopefully this free excerpt. The following excerpt is from SAS Press

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Ruth Dobson-TorresJanuary 23, 2014 0

Could SAS programming be in your future?

Even though I’ve worked as software technology marketer over the years, I have to admit that on a personal level I’ve probably related more to TV programming than software programming. When it comes to writing, I’ve always gravitated more toward crafting marketing communications than code. And when it comes to

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Rick WicklinJanuary 13, 2014 0

How to vectorize time series computations

Vector languages such as SAS/IML, MATLAB, and R are powerful because they enable you to use high-level matrix operations (matrix multiplication, dot products, etc) rather than loops that perform scalar operations. In general, vectorized programs are more efficient (and therefore run faster) than programs that contain loops. For an example

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Cynthia ZenderJanuary 7, 2014 0

What to do when a table’s not enough?

Sure, you have a great looking table and you produce it with PROC TABULATE. And then, bam! Your boss comes along and decides that since your output looks so good in Word, that he’d like that boilerplate paragraph inserted automatically. Currently, you produce the tables and then pass the RTF

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Rick WicklinDecember 16, 2013 0

How to coerce SAS/IML vectors to matrices

Recently a SAS/IML programmer asked a question regarding how to perform matrix arithmetic when some of the data are in vectors and other are in matrices. The programmer wanted to add the following matrices: The problem was that the numbers in the first two matrices were stored in vectors. The

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Rick WicklinDecember 9, 2013 0

Interpreting PROC IML error messages: Matrices do not conform to the operation

When learning a new language, it is important to learn to interpret error messages that come from the language's parser or compiler. Three years ago I blogged about how to interpret SAS/IML error messages. However, many questions have been posted to the SAS/IML Support Community that indicate that some people

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Catherine (Cat) Truxillo

Catherine (Cat) TruxilloDecember 2, 2013 0

Two Ways to Handle Baselines in Catnip-Crazed Kitties

“Dear Cat, In a repeated measures drug study, I am unsure what to do with the baseline measurement. Since it is one of the time points in my study, I feel like I should use it as one of the dependent variable measurements. But I have seen analyses where baseline

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Rick WicklinDecember 2, 2013 0

Write a matrix in the "long form"

If you write an n x p matrix from PROC IML to a SAS data set, you'll get a data set with n rows and p columns. For some applications, it is more convenient to write the matrix in a "long format" with np observations and three columns. The first

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Rick WicklinNovember 18, 2013 0

Vectorizing the construction of a structured matrix

In using a vector-matrix language such as SAS/IML, MATLAB, or R, one of the challenges for programmers is learning how to vectorize computations. Often it is not intuitive how to program a computation so that you avoid looping over the rows and columns of a matrix. However, there are a

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Rick WicklinNovember 10, 2013 0

The GCD and LCM functions in SAS

My daughter's middle school math class recently reviewed how to compute the greatest common factor (GCF) and the least common multiple (LCM) of a set of integers. (The GCF is sometimes called the greatest common divisor, or GCD.) Both algorithms require factoring integers into a product of primes. While helping

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Rick WicklinOctober 30, 2013 0

Square root transformations: How to handle negative data values?

I was looking at someone else's SAS/IML program when I saw this line of code: y = sqrt(x<>0); The statement uses the element maximum operator (<>) in the SAS/IML language to make sure that negative value are never passed to the square root function. This little trick is a real

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Rick WicklinOctober 28, 2013 0

How to order categories in a two-way table with PROC FREQ

If you've ever tried to use PROC FREQ to create a frequency table of two character variables, you know that by default the categories for each variable are displayed in alphabetical order. A different order is sometimes more useful. For example, consider the following two-way table for the smoking status

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Rick WicklinOctober 21, 2013 0

Assign the diagonal elements of a matrix

SAS/IML programmers know that the VECDIAG matrix can be used to extract the diagonal elements of a matrix. For example, the following statements extract the diagonal of a 3 x 3 matrix: proc iml; m = {1 2 3, 4 5 6, 7 8 9}; v = vecdiag(m); /* v = {1,5,9}

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Rick WicklinOctober 18, 2013 0

Rotating matrices

This article is about rotating matrices. No, I don't mean "rotation matrices," I mean rotating matrices. As in turning a matrix 90 degrees in a clockwise or counterclockwise direction. I was reading a program written in MATLAB in which the programmer used a MATLAB function called ROT90, which rotates a

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Rick WicklinOctober 7, 2013 0

How to create a library of functions in PROC IML

What is the best way to share SAS/IML functions with your colleagues? Give them the source code? Create a function library that they can use? This article describes three techniques that make your SAS/IML functions accessible to others. As background, remember that you can define new functions and subroutines in

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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 | 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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Jim SimonSeptember 18, 2013 0

Importing CSV files into SAS datasets

Sometimes, your first impulse may not be correct, like trading in your practical sedan for a hot 2-seater. Other times, your first impulse is perfect, as in the examples below. Suppose the automobile data you wish to analyze resides in a CSV file. Naturally, your first impulse is to import

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Rick WicklinSeptember 13, 2013 0

The difference between frequencies and weights in regression analysis

This week I read an interesting blog post that led to a discussion about specifying the frequencies of observations in a regression model. In SAS software, many of the analysis procedures contain a FREQ statement for specifying frequencies and a WEIGHT statement for specifying weights in a weighted regression. Theis

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Jeff ThompsonSeptember 3, 2013 0

My transition from academia to SAS

I am passionate about teaching. My colleagues would probably say this is the understatement of the year. And it likely has something to do with the fact that both of my parents were teachers. I started my teaching career at the university level and after many years an unexpected opportunity

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Rick WicklinSeptember 3, 2013 0

Convert a string into a vector of characters

Sometimes it is useful in the SAS/IML language to convert a character string into a vector of one-character values. For example, you might want to count the frequency distribution of characters, which is easy when each character is an element of a vector. The question of how to convert a

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PROC TEMPLATE Made Easy

Shelly GoodinAugust 30, 2013 0

SAS author's tip: Using pre-defined styles

This week's SAS tip is from Kevin D. Smith and his new book PROC TEMPLATE Made Easy: A Guide for SAS Users. Kevin is a software developer at SAS with extensive experience supporting PROC TEMPLATE and underlying ODS technologies. We're excited that Kevin decided to write his book and hope

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Rick WicklinAugust 26, 2013 0

Determine the version of SAS software at run time

Recently I wrote about how to determine the age of your SAS release. Experienced SAS programmers know that you can programatically determine information about your SAS release by using certain automatic macro variables that SAS provides: SYSVER: contains the major and minor version of the SAS release SYSVLONG: contains the

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Rick WicklinAugust 19, 2013 0

Errors that cause SAS to "freeze"... and what to do about them

Even the best programmers make mistakes. For most errors, SAS software displays the nature and location of the error, returns control to the programmer, and awaits further instructions. However, there are a handful of insidious errors that cause SAS to think that a statement or program is not finished. For

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Michelle HomesAugust 6, 2013 0

Read what you need

With the pervasiveness of mobile devices, being able to read while “on the go” has been easier than ever. How many times have you found yourself in a situation where you pass the time waiting by reading something on your phone/iPad/tablet etc? With eBooks on my iPad, I find that

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Rick WicklinAugust 2, 2013 0

How old is your version of SAS? Release dates for SAS software

How old is your version of SAS software? The graph on the left shows the release dates for various releases of SAS software, beginning with SAS 8.0. The graph is based on a graph on Jiangtang Hu's blog that shows the major SAS releases. As this graph demonstrates, SAS software

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Rick WicklinJuly 29, 2013 0

Read data sets that are specified by an array of names

One of my favorite features of SAS/IML 12.1 (released with 9.3m2) is that the USE and CLOSE statements support reading data set names that are specified in a SAS/IML matrix. The IMLPlus language in SAS/IML Studio has supported this syntax since the early 2000s, so I am pleased that this

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