useR! 2009 conference, Rennes, France

August 2, 2009
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Since my last attendance of the useR conference in Vienna, Austria, I have always wanted to go back. However, the high registration fee was always the factor that chills me off.This year, I am taking advantage of my last year as the student (the regis...

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useR! 2009 conference, Rennes, France

August 2, 2009
By

Since my last attendance of the useR conference in Vienna, Austria, I have always wanted to go back. However, the high registration fee was always the factor that chills me off.This year, I am taking advantage of my last year as the student (the regis...

Read more »

Example 7.8: Plot two empirical cumulative density functions using available tools

August 1, 2009
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Example 7.8: Plot two empirical cumulative density functions using available tools

The empirical cumulative density function (CDF) (section 5.1.16) is a useful way to compare distributions between populations. The Kolmogorov-Smirnov (section 2.4.2) statistic D is the value of x with the maximum distance between the two curves. As an...

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Simple visualization of a 11X5 table (for WordPress 2.9 Features Vote Results)

July 31, 2009
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Simple visualization of a 11X5 table (for WordPress 2.9 Features Vote Results)

I guess this is not the number one post I would like to start with on this blog, but I feel the time is right for it (community-wise). I’ll move on to the subject matter in a moment, but first a short intro: This blog is written by Tal Galili. I am an aspiring statistician who

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Simple visualization of a 11X5 table (for WordPress 2.9 Features Vote Results)

July 31, 2009
By
Simple visualization of a 11X5 table (for WordPress 2.9 Features Vote Results)

I guess this is not the number one post I would like to start with on this blog, but I feel the time is right for it (community-wise). I’ll move on to the subject matter in a moment, but first a short intro: This blog is written by Tal Galili. I am ...

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Kruskal-Wallis one-way analysis of variance

July 31, 2009
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If you have to perform the comparison between multiple groups, but you can not run a ANOVA for multiple comparisons because the groups do not follow a normal distribution, you can use the Kruskal-Wallis test, which can be applied when you can not make ...

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Kruskal-Wallis one-way analysis of variance

July 31, 2009
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If you have to perform the comparison between multiple groups, but you can not run a ANOVA for multiple comparisons because the groups do not follow a normal distribution, you can use the Kruskal-Wallis test, which can be applied when you can not make ...

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Analysis of variance: ANOVA, for multiple comparisons

July 30, 2009
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Analysis of variance: ANOVA, for multiple comparisonsThe ANOVA model can be used to compare the mean of several groups with each other, using a parametric method (assuming that the groups follow a Gaussian distribution).Proceed with the following example:The manager of a supermarket chain wants to see if the consumption in kilowatts of 4 stores between them are equal. He...

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Analysis of variance: ANOVA, for multiple comparisons

July 30, 2009
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Analysis of variance: ANOVA, for multiple comparisonsThe ANOVA model can be used to compare the mean of several groups with each other, using a parametric method (assuming that the groups follow a Gaussian distribution).Proceed with the following example:The manager of a supermarket chain wants to see if the consumption in kilowatts of 4 stores between them are equal. He...

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Comparison of two proportions: parametric (Z-test) and non-parametric (chi-squared) methods

July 29, 2009
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Consider for example the following problem.The owner of a betting company wants to verify whether a customer is cheating or not. To do this want to compare the number of successes of one player with the number of successes of one of his employees, of w...

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Comparison of two proportions: parametric (Z-test) and non-parametric (chi-squared) methods

July 29, 2009
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Consider for example the following problem.The owner of a betting company wants to verify whether a customer is cheating or not. To do this want to compare the number of successes of one player with the number of successes of one of his employees, of w...

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Wilcoxon signed rank test

July 29, 2009
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Non-parametric statistical hypothesis test, for the comparison of the means between 2 paired samplesThe mayor of a city wants to see if pollution levels are reduced by closing the streets to the car traffic. This is measured by the rate of pollution every 60 minutes (8am 22pm: total of 15 measurements) in a day when traffic is open, and...

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Wilcoxon signed rank test

July 29, 2009
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Non-parametric statistical hypothesis test, for the comparison of the means between 2 paired samplesThe mayor of a city wants to see if pollution levels are reduced by closing the streets to the car traffic. This is measured by the rate of pollution every 60 minutes (8am 22pm: total of 15 measurements) in a day when traffic is open, and...

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Beta Verson of tikzDevice Released!

July 28, 2009
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The tikzDevice package provides a new graphics device for R which enables direct output of graphics in a LaTeX-friendly way. The device output consists of files containing instructions for the TikZ graphics language and may be imported directly into LaTeX documents using the \input{} command. The beta version of tikzDevice is now available here. An

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I know it’s been so long…

July 28, 2009
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Hey,I know it's been so long since last time I posted something in here, but I was really busy with my thesis and some other stuff, but now that I have more time I promise I'll post some interesting stuff in here, by the way, I found such an Interestin...

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I know it’s been so long…

July 28, 2009
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Hey,I know it's been so long since last time I posted something in here, but I was really busy with my thesis and some other stuff, but now that I have more time I promise I'll post some interesting stuff in here, by the way, I found such an Interestin...

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Corpus Linguistics with R, Day 2

July 28, 2009
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R Lesson 2 text gsub ("second", "third", text) SEARCH-REPLACE-SUBJECT "This is a first example sentence." "And this is a third example sentence." > gsub ("n", "X", text) "This is a first example seXteXce." "AXd this is a secoXd example seXteXce." > gsub ("is", "was", text) "Thwas was a first example

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Corpus Linguistics with R, Day 1

July 28, 2009
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(This post documents the first day of a class on R that I took at ESU C&T. I is posted here purely for my own use.) R Lesson 1 > 2+3; 2/3; 2^3 5 0.6666667 8 --- Fundamentals - Functions > log(x=1000, base=10) 3 --- (Formals describes the syntax of other

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Wilcoxon-Mann-Whitney rank sum test (or test U)

July 27, 2009
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Comparison of the averages of two independent groups of samples, of which we can not assume a distribution of Gaussian type; is also known as Mann-Whitney U-test.You want to see if the mean of goals suffered by two football teams over the years is the same. Are below the number of goals suffered by each team in 6 games...

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Wilcoxon-Mann-Whitney rank sum test (or test U)

July 27, 2009
By

Comparison of the averages of two independent groups of samples, of which we can not assume a distribution of Gaussian type; is also known as Mann-Whitney U-test.You want to see if the mean of goals suffered by two football teams over the years is the same. Are below the number of goals suffered by each team in 6 games...

Read more »

Beautiful Data

July 27, 2009
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Beautiful Data

O'Reilly's recent publication Beautiful Data has a chapter by Jeff Jonas which is enough reason in itself for me to recommend it. The chapter, Data Finds Data, is also available as a PDF download.

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Beautiful Data

July 27, 2009
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Beautiful Data

O'Reilly's recent publication Beautiful Data has a chapter by Jeff Jonas which is enough reason in itself for me to recommend it. The chapter, Data Finds Data, is also available as a PDF download.

Read more »

R Snippet for Sampling from a Dataframe

July 27, 2009
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It took me a while to figure this out, so I thought I'd share. I have a dataframe with millions of observations in it, and I want to estimate a density distribution, which is a memory intensive process. Running my kde2d function on the full dataframe throws and error -- R tries to allocate a vector that...

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biomaRt

July 27, 2009
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I use R and Bioconductor for most of my work. I am also increasingly replacing things I would have done before in Perl with R. One such example of this is the Bioconductor module biomaRt.As the name suggest it allows for access to BioMart via R. BioMart is a method of accessing large online databases...

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biomaRt

July 27, 2009
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I use R and Bioconductor for most of my work. I am also increasingly replacing things I would have done before in Perl with R. One such example of this is the Bioconductor module biomaRt.As the name suggest it allows for access to BioMart via R. BioMart is a method of accessing large online databases...

Read more »

Book now shipping from Amazon

July 27, 2009
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Book now shipping from Amazon

Amazon now reports that the book is in stock! The current discount is 13%.Or, order from the publisher. If you are an ASA member, you can use the online discount code 634LH to obtain a 15% discount.

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Paired Student’s t-test

July 26, 2009
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Paired Student’s t-test

Comparison of the means of two sets of paired samples, taken from two populations with unknown variance.A school athletics has taken a new instructor, and want to test the effectiveness of the new type of training proposed by comparing the average time...

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Select operations on R data frames

July 26, 2009
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Select operations on R data frames

The R language is weird - particularly for those coming from a typical programmer's background, which likely includes OO languages in the curly-brace family and relational databases using SQL. A key data structure in R, the data.frame, is used somethin...

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Rosetta Code

July 26, 2009
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Rosetta Code

Today I'd like to suggest the interesting Rosetta Code site:Rosetta Code is a programming chrestomathy site. The idea is to present solutions to the same task in as many different languages as possible, to demonstrate how languages are similar and diff...

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