Articles by Ralph

Useful functions for data frames

August 9, 2010 | Ralph

The R software system is primarily command line based so when there are large sets of data it is not easy to browse the data frames. There are various useful functions for working with data frames. For example, after loading data from a text file we might want to view ... [Read more...]

Creating a Presentation with LaTeX Beamer – Boxes

July 19, 2010 | Ralph

We can add coloured boxes with text or mathematics into a LaTeX beamer presentation which is particularly useful if we have definitions, theorem or computer code to highlight this information that may not be so accessible within a paragraph of text. Fast Tube by Casper The easiest way to create ...
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Generating Balanced Incomplete Block Designs (BIBD)

July 16, 2010 | Ralph

The Balanced Incomplete Block Design (BIBD) is a well studied experimental design that has various desirable features from a statistical perspective. The crossdes package in R provides a way to generate a block design for some given parameters and test wheter this design satisfies the BIBD conditions. For a BIBD ... [Read more...]

Creating a Presentation with LaTeX Beamer – Tables

July 14, 2010 | Ralph

Tables of information can be included in a LaTeX beamer presentation in the same way that they would be incorporated into any other LaTeX document. The tabular environment is used and, if necessary, the tables could be numbered but this probably doesn’t make as much sense as labelling and ...
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Creating a Presentation with LaTeX Beamer – Getting Started

July 2, 2010 | Ralph

The LaTeX beamer package can be used to create appealing presentations for many applications. A working knowledge of LaTeX is required but once the initial learning curve and transition is made from a visual word processor to a markup based approach the benefits are worth the initial investment of time. ... [Read more...]

R Commander – two-way analysis of variance

June 25, 2010 | Ralph

Two way analysis of variance models can be fitted to data using the R Commander GUI. The general approach is similar to fitting the other types of model in R Commander described in previous posts. Fast Tube by Casper The “Statistics” menu provides access to some analysis of variance models ... [Read more...]

R Commander – one-way analysis of variance

June 25, 2010 | Ralph

One way analysis of variance models can be fitted to data using the R Commander GUI. The general approach is similar to fitting the other types of model in R Commander described in previous posts. Fast Tube by Casper The “Statistics” menu provides access to some analysis of variance models ... [Read more...]

R Commander – logistic regression

June 23, 2010 | Ralph

We can use the R Commander GUI to fit logistic regression models with one or more explanatory variables. There are also facilities to plot data and consider model diagnostics. The same series of menus as for linear models are used to fit a logistic regression model. Fast Tube by Casper ... [Read more...]

R Commander – linear regression

June 18, 2010 | Ralph

We can fit various linear regression models using the R Commander GUI which also provides various ways to consider the model diagnostics to determine whether we need to consider a different model. Fast Tube by Casper The “Statistics” menu provides access to various statistical models via the “Fit models” sub-menu ... [Read more...]

R Commander – hypothesis testing

June 16, 2010 | Ralph

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 ... [Read more...]

R Commander – data manipulation and summaries

June 13, 2010 | Ralph

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 ... [Read more...]

R Commander – a good introductory GUI for R

June 1, 2010 | Ralph

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 ... [Read more...]

Creating surface plots

May 28, 2010 | Ralph

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 ...
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Variable selection using automatic methods

May 22, 2010 | Ralph

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 ... [Read more...]

Linear regression models with robust parameter estimation

May 15, 2010 | Ralph

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 ... [Read more...]

Manual variable selection using the dropterm function

May 12, 2010 | Ralph

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 ...
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