Posts Tagged ‘ Getting Started ’

The relationship between skewness and kurtosis

January 28, 2015
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The relationship between skewness and kurtosis

In my book Simulating Data with SAS, I discuss a relationship between the skewness and kurtosis of probability distributions that might not be familiar to some statistical programmers. Namely, the skewness and kurtosis of a probability distribution are not independent. If κ is the full kurtosis of a distribution and […]

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IF-THEN logic with matrix expressions

January 26, 2015
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IF-THEN logic with matrix expressions

In the SAS DATA step, all variables are scalar quantities. Consequently, an IF-THEN/ELSE statement that evaluates a logical expression is unambiguous. For example, the following DATA step statements print "c=5 is TRUE" to the log if the variable c is equal to 5: if c=5 then put "c=5 is TRUE"; […]

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What is an empty matrix?

January 22, 2015
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What is an empty matrix?

At the beginning of my book Statistical Programming with SAS/IML Software I give the following programming tip (p. 25): Do not confuse an empty matrix with a matrix that contains missing values or with a zero matrix. An empty matrix has no rows and no columns. A matrix that contains […]

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Finding matrix elements that satisfy a logical expression

January 20, 2015
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Finding matrix elements that satisfy a logical expression

A common task in SAS/IML programming is finding elements of a SAS/IML matrix that satisfy a logical expression. For example, you might need to know which matrix elements are missing, are negative, or are divisible by 2. In the DATA step, you can use the WHERE clause to subset data. […]

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Compute the kth smallest data value in SAS

January 7, 2015
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Compute the kth smallest data value in SAS

A SAS programmer recently posted a question to the SAS/IML Support Community about how to compute the kth smallest value in a vector of numbers. In the DATA step, you can use the SMALLEST function to find the smallest value in an array, but there is no equivalent built-in function […]

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Elementwise minimum and maximum operators

December 15, 2014
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Elementwise minimum and maximum operators

Like most programming languages, the SAS/IML language has many functions. However, the SAS/IML language also has quite a few operators. Operators can act on a matrix or on rows or columns of a matrix. They are less intuitive, but can be quite powerful because they enable you perform computations without […]

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The direct product (Kronecker product) in SAS

December 8, 2014
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The direct product (Kronecker product) in SAS

There are many ways to multiply scalars, vectors, and matrices, but the Kronecker product (also called the direct product) is multiplication on steroids. The Kronecker product looks scary, but it is actually simple. The Kronecker product is merely a way to pack multiples of a matrix B into a block […]

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Compute maximum and minimum values for rows and columns in SAS

December 1, 2014
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Compute maximum and minimum values for rows and columns in SAS

A common question on SAS discussion forums is how to compute the minimum and maximum values across several variables. It is easy to compute statistics across rows by using the DATA step. This article shows how to compute the minimum and maximum values for each observation (across variables) and, for […]

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Overview of new features in SAS/IML 13.1

November 24, 2014
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Overview of new features in SAS/IML 13.1

SAS software contains a lot of features, and each release adds more.To make sure that you do not miss new features that appear in the SAS/IML language, the word cloud on the right sidebar of my blog contains numbers that relate to SAS or SAS/IML releases. For example, you can […]

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The difference between RUN and CALL for SAS/IML subroutines

November 17, 2014
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The difference between RUN and CALL for SAS/IML subroutines

Have you ever noticed that some SAS/IML programmers use the CALL statement to call a subroutine, whereas others use the RUN statement? Have you ever wondered why the SAS/IML language has two statements that do the same thing? It turns out that the CALL statement and the RUN statement do […]

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