307 search results for "ANOVA"

Count data: To Log or Not To Log

July 22, 2015
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Count data: To Log or Not To Log

Count data are widely collected in ecology, for example when one count the number of birds or the number of flowers. These data follow naturally a Poisson or negative binomial distribution and are therefore sometime tricky to fit with standard LMs. A traditional approach has been to log-transform such data and then fit LMs to

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Connecting R to Everything with IFTTT

June 18, 2015
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Connecting R to Everything with IFTTT

IFTTT ("if this then that") is one of my favorite tools. I use it to keep and share articles, turn on my home's lights at sundown, alert me when certain keywords are mentioned on Twitter/Reddit/etc., and many other things. Recently, the great people at IFTTT announced the Maker Channel, which allows recipes to make and receive web requests. This...

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advanced.procD.lm for pairwise tests and model comparisons

June 9, 2015
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In geomorph 2.1.5, we decided to deprecate the functions, pairwiseD.test and pairwise.slope.test.   Our reason for this was two-fold.  First, recent updates by CRAN rendered these functions unstable.  These functions depended on the mode...

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Paper Helicopter Experiment, part III

May 31, 2015
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Paper Helicopter Experiment, part III

As final part of my paper helicopter experiment analysis (part I, part II) I do a reanalysis for one more data set. In 2002 Erik Erhardt and Hantao Mai did an extensive experiment, see The Search for the Optimal Paper Helicopter. They did a number of s...

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An R Enthusiast Goes Pythonic!

May 28, 2015
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An R Enthusiast Goes Pythonic!

I’ve spent so many years using and broadcasting my love for R and using Python quite minimally. Having read recently about machine learning in Python, I decided to take on a fun little ML project using Python from start to … Continue reading →

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Simulation-based power analysis using proportional odds logistic regression

May 22, 2015
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Simulation-based power analysis using proportional odds logistic regression

Consider planning a clinicial trial where patients are randomized in permuted blocks of size four to either a 'control' or 'treatment' group. The outcome is measured on an 11-point ordinal scale (e.g., the numerical rating scale for pain). It may be reasonable to evaluate the results of this trial using a proportional odds cumulative logit

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The perfect t-test

May 18, 2015
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The perfect t-test

I've created an easy to use R script that will import your data, and performs and writes up a state-of-the-art dependent or independent t-test. The goal of this script is to examine whether more researcher-centered statistical tools (i.e., a one-click analysis script that checks normality assumptions, calculates effect sizes and their confidence intervals, creates good figures,...

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Tips & Tricks 8: Examining Replicate Error

April 4, 2015
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Geomorph users,When starting out in a geometric morphometrics study, the common questions are ones of repeatability and measurement error.How much of the variation in the Procrustes residuals is due to human (digitizing) error? How much is du...

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Recruitment Chapter for IFAR

April 2, 2015
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Recruitment Chapter for IFAR

I have added a very rough draft of the Recruitment chapter to the Introduction to Fisheries Analysis with R (IFAR) page.  This chapter is a complete re-working of the old Stock-Recruitment vignette and includes a section on fitting non-linear stock-recruitment … Continue reading →

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Geomorph and Multivariate Datasets

March 25, 2015
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Did you know that geomorph is not just for landmark-based geometric morphometric (shape) data?We are committed to providing statistical tools for multivariate AND multidimensional morphometric data.As laid out in the recent series of papers on Phylogenetic Comparative Methods for high-dimensional data (Adams 2014a, Adams 2014b, Adams 2014c, Adams & Felice 2014), harnessing the R-mode – Q-mode equivalency as first shown...

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