Blog Archives

R Commander – hypothesis testing

June 16, 2010
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R Commander – hypothesis testing

The R Commander GUI can be used to perform classical hypothesis testing. There are menu options to undertake the variants on the t-test as well as tests on proportions or equality of variances for two samples of data. Fast Tube by Casper The “Statistics” menu provides access to various hypothesis tests via the “Means” sub-menu including: Single sample

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R Commander – data manipulation and summaries

June 13, 2010
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R Commander – data manipulation and summaries

Previously we considered the R Commander interface as a simple GUI for the R statistical software system. Here we will look at how to undertake data manipulation and creating basic statistical summaries of data sets. Fast Tube by Casper The R Commander GUI has two menus “Data” and “Statistics” that are used for manipulating data sets and

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R Commander – a good introductory GUI for R

June 1, 2010
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R Commander – a good introductory GUI for R

The R software is very powerful and flexible but one of the complaints of new users is that the learning curve is steep and can be daunting. There have been various projects to create GUIs for R with varying levels of sophistication, one of which is R Commander by John Fox. Fast Tube by Casper This interface

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Creating surface plots

May 28, 2010
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Creating surface plots

A 3d wireframe plot is a type of graph that is used to display a surface – geographic data is an example of where this type of graph would be used or it could be used to display a fitted model with more than one explanatory variable. These plots are related to contour plots which

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Variable selection using automatic methods

May 22, 2010
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When we have a set of data with a small number of variables we can easily use a manual approach to identifying a good set of variables and the form they take in our statistical model. In other situations we may have a large number of potentially important variables and it soon becomes a time

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Linear regression models with robust parameter estimation

May 15, 2010
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There are situations in regression modelling where robust methods could be considered to handle unusual observations that do not follow the general trend of the data set. There are various packages in R that provide robust statistical methods which are summarised on the CRAN Robust Task View. As an example of using robust statistical estimation in

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Manual variable selection using the dropterm function

May 12, 2010
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Manual variable selection using the dropterm function

When fitting a multiple linear regression model to data a natural question is whether a model can be simplified by excluding variables from the model. There are automatic procedures for undertaking these tests but some people prefer to follow a more manual approach to variable selection rather than pressing a button and taking what comes

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Book Review – Modern Applied Statistics with S by W. N. Venables and B. D. Ripley (Springer 2003)

May 9, 2010
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Book Review – Modern Applied Statistics with S by W. N. Venables and B. D. Ripley (Springer 2003)

Order this book from Amazon Modern Applied Statistics with S (Fourth Edition) is one of the oldest and most popular books on Applied Statistics using R and S-plus. A large number of topics in Applied Statistics are covered in this book and it is certainly not for the faint hearted. A sound knowledge of

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Using the update function during variable selection

May 9, 2010
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When fitting statistical models to data where there are multiple variables we are often interested in adding or removing terms from our model and in cases where there are a large number of terms it can be quicker to use the update function to start with a formula from a model that we have already

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Displaying data using level plots

May 3, 2010
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Displaying data using level plots

A level plot is a type of graph that is used to display a surface in two rather than three dimensions – the surface is viewed from above as if we were looking straight down and is an alternative to a contour plot – geographic data is an example of where this type of graph

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