Blog Archives

Adding Percentiles to PDQ

April 22, 2013
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Adding Percentiles to PDQ

Pretty Damn Quick (PDQ) performs a mean value analysis of queueing network models: mean values in; mean values out. By mean, I mean statistical mean or average. Mean input values include such queueing metrics as service times and arrival rates. These could be sample means. Mean output values include such queueing metrics as waiting time and queue...

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Upcoming GDAT Class May 6-10, 2013

April 22, 2013
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Upcoming GDAT Class May 6-10, 2013

Enrollments are still open for the Level III Guerrilla Data Analysis Techniques class to be held during the week May 6—10. Early-bird discounts are still available. Enquire when you register. As usual, all classes are held at our lovely Larkspur...

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Extracting the Epidemic Model: Going Beyond Florence Nightingale Part II

February 7, 2013
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Extracting the Epidemic Model: Going Beyond Florence Nightingale Part II

This is the second of a two part reexamination of Florence Nightingale's data visualization based on her innovative cam diagrams (my term) shown in Figure 1. Figure 1. Nightingale's original cam diagrams (click to enlarge)RecapIn Part I, I showed that FN applied sectoral areas, rather than a pie chart or...

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Going Beyond Florence Nightingale’s Data Diagram: Did Flo Blow It with Wedges?

January 23, 2013
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Going Beyond Florence Nightingale’s Data Diagram: Did Flo Blow It with Wedges?

In 2010, I wrote a short blog item about Florence Nightingale the statistician, solely because of its novelty value. I didn't even bother to look closely at the associated graphic she designed, but that's what I intend to do here. In this first installment, I reflect on her famous data visualization by reconstructing it...

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The Social Network Ranking is Wrong

January 14, 2013
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The Social Network Ranking is Wrong

Call me old-fashioned, but I never saw the movie The Social Network until last year (at a private screening). In case you also missed it, it's the Hollywood version of how Facebook.com came into being. Quite apart from any artistic criticisms, I have a genuine psychological problem with movies like TSN. I keep getting caught up...

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PDQ 6.0 is On Its Way

November 12, 2012
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PDQ (Pretty Damn Quick) version 6.0.β is in the QA pipeline. Although this is a major release, cosmetically, things won't look any different when it comes to writing PDQ models. All the big changes have taken place under the hood in order to make PDQ more consistent with the R statistical environment. R version 2.15.2...

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PostgreSQL Scalability Analysis Deconstructed

April 11, 2012
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PostgreSQL Scalability Analysis Deconstructed

In 2010, I presented my universal scalability law (USL) at the SURGE conference. I came away with the impression that nobody really understood what I was talking about (quantifying scalability) or, maybe DevOps types thought it was all too hard (math). Since then, however, I've come to find out that people like Baron Schwartz did get it...

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How to Generate Exponential Delays

March 21, 2012
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How to Generate Exponential Delays

This question arose while addressing Comments on a previous blog post about exponentially distributed delays. One of my ongoing complaints is that many, if not most, popular load-test generation tools do not provide exponential variates as part of a library of time delays or think-time distributions. Not only is this situation bizarre, given that all load tests...

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Green Disk Sizing

February 3, 2012
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Green Disk Sizing

I finally got around to completing item 5 on my 2011 list concerning electrical power consumed by a magnetic hard disk drive (HDD). The semi-empirical statement is: Power ∝ Nplatters × Ω2.8 × D4.6    . . .    (1) where Nplatters is the number of platters on the spindle, Ω is the rotational speed in revolutions per minute (RPM) and D...

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Visual Illusions: Google vs Facebook vs Yahoo

October 3, 2011
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Visual Illusions: Google vs Facebook vs Yahoo

The ability to visualize data, enabled by the advent of graphical computer tools, has been a great boon to Cap and Perf. The power derives from the way graphical displays provide an efficient impedance match to the visual system in our brain. The weakness derives from the way graphical displays provide an efficient impedance match to the visual system...

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