Blog Archives

Example 7.23: the Monty Hall problem

January 20, 2010
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Example 7.23: the Monty Hall problem

The Monty Hall problem illustrates a simple setting where intuition often leads to a solution different from formal reasoning. The situation is based on the game show Let's Make a Deal. First, Monty puts a prize behind one of three doors. Then the player chooses a door. Next, (without moving the pize) Monty opens an...

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Example 7.21: Write a function to simulate categorical data

January 8, 2010
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Example 7.21: Write a function to simulate categorical data

In example 7.20, we showed how to simulate categorical data. But we might anticipate needing to do that frequently. If a SAS function weren't built in and an equivalent R function not available in a package, we could build them from scratch.SASThe SAS code is particularly tortured, since we must parse the parameter string to extract the...

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Example 7.20: Simulate categorical data

January 4, 2010
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Example 7.20: Simulate categorical data

Both SAS and R provide means of simulating categorical data (see section 1.10.4). Alternatively, it is trivial to write code to do this directly. In this entry, we show how to do it once. In a future entry, we'll demonstrate writing a SAS Macro (section A.8.1) and a function in R (section B.5.2) to do it...

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Example 7.19: find the closest pair of observations

December 28, 2009
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Example 7.19: find the closest pair of observations

Suppose we need to find the closest pair of observations on some variable x. For example, we might be concerned that some data had been accidentally duplicated. We return the ID's of the two closest observations, and their distance from each other. In both languages, we'll first create the data, then sort it, recognizing that the...

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SAS and R included on R bloggers

December 18, 2009
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SAS and R included on R bloggers

The R bloggers site is an aggregator for blogs about R. We're excited to be joining that community and suggest any readers of this blog may also find it useful.

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Example 7.18: Displaying missing value categories in a table

December 14, 2009
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Example 7.18: Displaying missing value categories in a table

When displaying contingency tables (section 2.3.1), there are times when it is useful to either show or hide the missing data category. Both SAS and the typical R command default to displaying the table only for observations where both factors are observed.In this example, we generate some multinomial data (section 1.10.4) and then produce tables with and without...

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Example 7.15: A more complex sales graphic

October 13, 2009
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Example 7.15: A more complex sales graphic

The plot of Amazon sales rank over time generated in example 7.14 leaves questions. From a software perspective, we'd like to make the plot prettier, while we can embellish the plot to inform our interpretation about how the rank is calculated.For the latter purpose, we'll create an indicator of whether the rank was recorded in nighttime (eastern US...

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Example 7.14: A simple graphic of sales

September 29, 2009
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Example 7.14: A simple graphic of sales

In this example, we show a simple plot of the sales rank data read in as shown in example 7.13.SASIn SAS, we use the symbol statement (section 5.3) to request small (with the h option) dots (with the v option, and that the dots not be connected (with the i option. (See sections 5.2.2, 5.3.9 for more details.)we...

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Example 7.11: Plot an empirical cumulative distribution function from scratch

August 31, 2009
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Example 7.11: Plot an empirical cumulative distribution function from scratch

In example 7.8, we used built-in functions to produce an empirical CDF plot. But the empirical cumulative distribution function (CDF) is simple to calculate directly, and it might be useful to have more control over its appearance than is afforded by...

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Example 7.10: Get data from R into SAS

August 13, 2009
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Example 7.10: Get data from R into SAS

In our previous entry, we described how to generate a dataset from SAS that could be used for analyses in R. Alternatively, someone primarily using R might want to test the new ”statistical graphics” procedures available starting with SAS 9.2. Her...

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