Blog Archives

How to visualize a kernel density estimate

July 27, 2016
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How to visualize a kernel density estimate

A kernel density estimate (KDE) is a nonparametric estimate for the density of a data sample. A KDE can help an analyst determine how to model the data: Does the KDE look like a normal curve? Like a mixture of normals? Is there evidence of outliers in the data? In […] The post How to visualize a kernel density estimate appeared first on The DO Loop.

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Statistical model building and the SELECT procedures in SAS

July 25, 2016
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Statistical model building and the SELECT procedures in SAS

Last week I read an interesting paper by Bob Rodriguez: "Statistical Model Building for Large, Complex Data: Five New Directions in SAS/STAT Software." In it, Rodriguez summarizes five modern techniques for building predictive models and highlights recent SAS/STAT procedures that implement those techniques. The paper discusses the following high-performance (HP) […] The post Statistical model building and the SELECT procedures in SAS appeared first on The DO Loop.

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Do you write unnecessary SAS statements?

July 20, 2016
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Do you write unnecessary SAS statements?

I'm addicted to you. You're a hard habit to break. Such a hard habit to break. —  Chicago, "Hard Habit To Break" Habits are hard to break. For more than 20 years I've been putting semicolons at the end of programming statements in SAS, C/C++, and Java/Javascript. But lately I've been […] The post Do you write unnecessary SAS statements? appeared first on The DO Loop.

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Color markers in a scatter plot by a third variable in SAS

July 18, 2016
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Color markers in a scatter plot by a third variable in SAS

One of my favorite new features in PROC SGPLOT in SAS 9.4m2 is addition of the COLORRESPONSE= and COLORMODEL= options to the SCATTER statement. By using these options, it is easy to color markers in a scatter plot so that the colors indicate the values of a continuous third variable. […] The post Color markers in a scatter plot by a third variable in SAS appeared first on The DO…

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Absorbing Markov chains in SAS

July 13, 2016
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Absorbing Markov chains in SAS

Last week I showed how to represent a Markov transition matrix in the SAS/IML matrix language. I also showed how to use matrix multiplication to iterate a state vector, thereby producing a discrete-time forecast of the state of the Markov chain system. This article shows that the expected behavior of […] The post Absorbing Markov chains in SAS appeared first on The DO Loop.

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Break a sentence into words in SAS

July 11, 2016
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Break a sentence into words in SAS

Two of my favorite string-manipulation functions in the SAS DATA step are the COUNTW function and the SCAN function. The COUNTW function counts the number of words in a long string of text. Here "word" means a substring that is delimited by special characters, such as a space character, a […] The post Break a sentence into words in SAS appeared first on The DO Loop.

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Markov transition matrices in SAS/IML

July 7, 2016
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Markov transition matrices in SAS/IML

Many computations in elementary probability assume that the probability of an event is independent of previous trials. For example, if you toss a coin twice, the probability of observing "heads" on the second toss does not depend on the result of the first toss. However, there are situations in which […] The post Markov transition matrices in SAS/IML appeared first on The DO Loop.

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Cantor sets, the devil’s staircase, and probability

July 5, 2016
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Cantor sets, the devil’s staircase, and probability

Last week I blogged about how to draw the Cantor function in SAS. The Cantor function is used in mathematics as a pathological example of a function that is constant almost everywhere yet somehow manages to "climb upwards," thus earning the nickname "the devil's staircase." The Cantor function has three […] The post Cantor sets, the devil's staircase, and probability appeared first on The DO Loop.

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Visualize the Cantor function in SAS

June 29, 2016
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Visualize the Cantor function in SAS

I was a freshman in college the first time I saw the Cantor middle-thirds set and the related Cantor "Devil's staircase" function. (Shown at left.) These constructions expanded my mind and led me to study fractals, real analysis, topology, and other mathematical areas. The Cantor function and the Cantor middle-thirds […] The post Visualize the Cantor function in SAS appeared first on The DO Loop.

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In praise of simple graphics

June 27, 2016
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In praise of simple graphics

'Tis a gift to be simple. -- Shaker hymn In June 2015 I published a short article for Significance, a magazine that features statistical and data-related articles that are of general interest to a wide a range of scientists. The title of my article is "In Praise of Simple Graphics." […] The post In praise of simple graphics appeared first on The DO Loop.

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