Posts Tagged ‘ Uncategorized ’

How much do New Yorkers tip taxi drivers?

May 2, 2016
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How much do New Yorkers tip taxi drivers?

When I read Robert Allison's article about the cost of a taxi ride in New York City, I was struck by the scatter plot (shown at right; click to enlarge) that plots the tip amount against the total bill for 12 million taxi rides. The graph clearly reveals diagonal and […] The post How much do New Yorkers tip taxi drivers? appeared first on The DO Loop.

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Packages: A new way to share SAS/IML programs

April 27, 2016
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Packages: A new way to share SAS/IML programs

My previous post highlighted presentations at SAS Global Forum 2016 that heavily used SAS/IML software. Several of the authors clearly want to share their work with the wider SAS analytical community. They include their SAS/IML program in an appendix or mention a web site or email address from which the […] The post Packages: A new way to share SAS/IML programs appeared first on The DO Loop.

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Matrix computations at SAS Global Forum 2016

April 25, 2016
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Matrix computations at SAS Global Forum 2016

Last week I attended SAS Global Forum 2016 in Las Vegas. I and more than 5,000 other attendees discussed and shared tips about data analysis and statistics. Naturally, I attended many presentations that featured using SAS/IML software to implement advanced analytical algorithms. Several speakers showed impressive mastery of SAS/IML programming […] The post Matrix computations at SAS Global Forum 2016 appeared first on The DO Loop.

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Visualize missing data in SAS

April 20, 2016
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Visualize missing data in SAS

You can visualize missing data. It sounds like an oxymoron, but it is true. How can you draw graphs of something that is missing? In a previous article, I showed how you can use PROC MI in SAS/STAT software to create a table that shows patterns of missing data in […] The post Visualize missing data in SAS appeared first on The DO Loop.

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Examine patterns of missing data in SAS

April 18, 2016
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Examine patterns of missing data in SAS

Missing data can be informative. Sometimes missing values in one variable are related to missing values in another variable. Other times missing values in one variable are independent of missing values in other variables. As part of the exploratory phase of data analysis, you should investigate whether there are patterns […] The post Examine patterns of missing data in SAS appeared first on The DO Loop.

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First steps with monads in Scala

April 15, 2016
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First steps with monads in Scala

Introduction In the previous post I gave a quick introduction to some important concepts in functional programming, such as HOFs, closures, currying and partial application, and hopefully gave some insight into why these concepts might be useful in the context of scientific computing. Another concept that is very important in modern functional programming is that … Continue reading First steps with monads in Scala

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Stan Coding Corner: O(N) Change-Point Program with Clever Forward-Backward Calculation

April 14, 2016
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It’s so much fun to work in open source. Luke Wiklendt sent along this improved code for a change-point model calculation in Stan. With N data points in the time series, the version in the manual is O(N2), whereas the improved version is O(N). In practice, Luke says [the new code] results in a dramatic […] The post Stan Coding Corner: O(N) Change-Point Program with Clever Forward-Backward Calculation appeared first…

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Head-tail versus head-head: A counterintuitive property of coin tosses

April 13, 2016
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Head-tail versus head-head: A counterintuitive property of coin tosses

I saw an interesting mathematical result in Wired magazine. The original article was about mathematical research into prime numbers, but the article included the following tantalizing fact: If Alice tosses a [fair] coin until she sees a head followed by a tail, and Bob tosses a coin until he sees […] The post Head-tail versus head-head: A counterintuitive property of coin tosses appeared first on The DO Loop.

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Set attributes of markers in PROC SGPLOT by using ODS style elements

April 11, 2016
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Set attributes of markers in PROC SGPLOT by using ODS style elements

The SG procedures in SAS use aesthetically pleasing default colors, shapes, and styles, but sometimes it is necessary to override the default attributes. The MARKERATTRS= option enables you to override the default colors, symbols, and sizes of markers in scatter plots and other graphs. Similarly, the LINEATTRS= option enables you […] The post Set attributes of markers in PROC SGPLOT by using ODS style elements appeared first on The DO…

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Generate points uniformly inside a d-dimensional ball

April 6, 2016
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Generate points uniformly inside a d-dimensional ball

Last week I showed how to generate random points uniformly inside a 2-d circular region. That article showed that the distance of a point to the circle's center cannot be distributed uniformly. Instead, you should use the square root of a uniform variate to generate 2-D distances to the origin. […] The post Generate points uniformly inside a d-dimensional ball appeared first on The DO Loop.

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