Blog Archives

Read sas7bdat files in R with GGASoftware Parso library

September 12, 2014
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... using the new R package sas7bdat.parso. The software company GGASoftware has extended the work of myself and others on the sas7bdat R package by developing a Java library called Parso, which also reads sas7bdat files. They have worked out most of the remaining kinks. For example, the Parso library reads sas7bdat files with compressed

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Making inferences about unusual population quantities.

April 4, 2014
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Making inferences about unusual population quantities.

This post builds on my last: Alternatives to model diagnostics for statistical inference?, where I had claimed that we could make quality inferences about the best linear approximation to a quadratic relationship. The R code below implements such a scenario, to establish a framework for discussion. I have inserted comments to augment the code. set.seed(42)

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Alternatives to model diagnostics for statistical inference?

March 28, 2014
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Alternatives to model diagnostics for statistical inference?

Consider the problem of making statistical inferences, as opposed to predictions. The product of statistical inference is a probabilistic statement about a population quantity, for example a 100(1-)% confidence interval for a population median. In this context, the principal reason for diagnostics is to comfort ourselves about the quality of such inferences. For example, we

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Image CGI with R

March 24, 2014
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I received an email recently with a question about using R in the common gateway interface (CGI) framework to create and pass image data to the web browser. I posted to stackoverflow about this some time ago, but had forgotten the details. The trouble is that R's graphics devices only write image data to file,

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A Recipe for Trellis/Faceted Plots Using Base R Graphics

July 5, 2013
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A Recipe for Trellis/Faceted Plots Using Base R Graphics

I frequently use lattice and ggplot2 to create trellis/faceted graphics. But, I gave up using these packages in a recent application, where I had initially constructed a complex graphic using the base R plotting functions. When I later decided that I wanted a faceted version, there was a dilema: re-create the complex graphic using lattice

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Descending Text in Righthand Margin of R Graphics à la mtext

June 28, 2013
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Descending Text in Righthand Margin of R Graphics à la mtext

There was an R-help thread in January regarding text in the righthand margin of an R graphic, where the text should be rendered in reading order from top to bottom. The base R function mtext is used to plot text in the margin. But, mtext is only able to render text from left to right

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Hurray! An R Connections API!

April 3, 2013
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I waited until April 3 to post this, so it wouldn't be taken as an April Fool's joke! A recent R News item announces that we now have a bona fide mechanism to create custom connections in R! This makes it possible to implement a custom connection in an R package. Until now, the only

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Identify 2/3 vacation photos, win $5 Starbucks gift card

March 29, 2013
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Identify 2/3 vacation photos, win $5 Starbucks gift card

I have a $5 Starbucks gift card that I simply can't remember to use; I've had it since Christmas. So, I will mail it (within the U.S.A.) to the first commenter who can identify the longitude/latitude (within 5km) where two of these three vacation photos were taken (photos below). ***Update 3/30/2013: locations A and C

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Generalized Pairs Plot: It’s about time!

March 28, 2013
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Generalized Pairs Plot: It’s about time!

JW Emerson, WA Green, B Schloerke, J Crowley, D Cook, H Hofmann, H Wickham (2013) The Generalized Pairs Plot. Journal of Computational and Graphical Statistics 22(1). Here's a free preprint version. Until this new paper and implementation by Emerson et al., there were no widely available pairs plots that accommodated both numerical and categorical fields.

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Simulated Power/Precision Analysis

February 21, 2013
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Simulated Power/Precision Analysis

I cringe when I see research proposals that describe a sophisticated statistical approach, yet do not evaluate this approach in their power/precision/sample size planning. It's often the case that a simplified version of the proposed statistical approach is used instead. Presumably, this is due to the limited availability of power/precision/sample size planning software for sophisticated

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