268 search results for "pca"

Summarising multivariate palaeoenvironmental data

January 9, 2014
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Summarising multivariate palaeoenvironmental data

The horseshoe effect is a well known and discussed issue with principal component analysis (PCA) (e.g. Goodall 1954; Swan 1970; Noy-Meir & Austin 1970). Similar geometric artefacts also affect correspondence analysis (CA). In part 1 of this series I looked at the implications of these “artefacts” for the recovery of temporal or single dominant gradients from multivariate palaeoecological data....

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Decluttering ordination plots part 4: orditkplot()

December 31, 2013
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Decluttering ordination plots part 4: orditkplot()

Earlier in this series I looked at the ordilabel() and then the orditorp() functions, and most recently the ordipointlabel() function in the vegan package as means to improve labelling in ordination plots. In this, the fourth and final post in the series I take a look at orditkplot(). If you’ve created ordination diagrams before or...

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Summarising multivariate palaeoenvironmental data

December 28, 2013
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Summarising multivariate palaeoenvironmental data

Ordination methods that yield orthogonal axes of variation are often used to summarise the multivariate data obtained from sediment cores. Usually the first or, less often, the first few ordination axes are taken as directions of change or the main patterns of variance in the multivariate data. There is an oft-overlooked issue with this approach that has the potential...

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Conditional dependence measures

December 17, 2013
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Conditional dependence measures

This week, I spend some time at the Workshop on Nonparametric Curve Smoothing conference at Concordia. Yesterday afternoon, Noël Veraverbeke show an interesting graph, to illustrate conditional copulas (and the derivation of conditional dependence measures, such as Kendall’s tau, or Spearman’s rho). A long time ago, in my PhD thesis (mainly on conditional copulas) I did try to derive conditional...

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The Complexities of Customer Segmentation: Removing Response Intensity to Reveal Response Pattern

December 15, 2013
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The Complexities of Customer Segmentation: Removing Response Intensity to Reveal Response Pattern

At the end of the last post, the reader was left assuming respondent homogeneity without any means for discovering if all of our customers adopted the same feature prioritization. To review, nine features were presented one at a time, and each time res...

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New version of analogue on CRAN

December 14, 2013
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It has been almost a year since the last release of the analogue package. At lot has happened in the intervening period and although I’ve been busy with a new job in a new country and coding on several other R packages, activity on analogue has also progressed a pace. As the version 0.12-0 of the package hits a...

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A note on the co-moments in the IFACD model

December 11, 2013
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The Independent Factor Autoregressive Conditional Density (IFACD) model of Ghalanos, Rossi and Urga (2014) uniquely, in its class of parametric models, generates time varying higher co-moment forecasts, as a consequence of the ACD specification of the conditional density of the standardized innovations. In this short note I discuss in more detail the properties of the

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A note on the co-moments in the IFACD model

December 11, 2013
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The Independent Factor Autoregressive Conditional Density (IFACD) model of Ghalanos, Rossi and Urga (2014) uniquely, in its class of parametric models, generates time varying higher co-moment forecasts, as a consequence of the ACD specification of the conditional density of the standardized innovations. In this short note I discuss in more detail the properties of the

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Using R to replicate common SPSS multiple regression output

December 4, 2013
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(This article was first published on Jeromy Anglim's Blog: Psychology and Statistics, and kindly contributed to R-bloggers) The following post replicates some of the standard output you might get from a multiple regression analysis in SPSS. A copy of the code in RMarkdown format is available on github. The post was motivated by this previous post that discussed using...

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sjPlot – data visualization for statistics (in social science) #rstats

November 26, 2013
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sjPlot – data visualization for statistics (in social science) #rstats

I’d like to announce the release of version 0.7 of my R package for data visualization and give a small overview of this package (download and installation instructions can be found on the package page). What does this package do? In short, the functions in this package mostly do two things: compute basic or advanced

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