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. Read the rest of this entry »
R Commander – linear regression
June 18th, 2010R Commander – hypothesis testing
June 16th, 2010The 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. Read the rest of this entry »
R Commander – data manipulation and summaries
June 14th, 2010Previously 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. Read the rest of this entry »
R Commander – a good introductory GUI for R
June 1st, 2010The 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. Read the rest of this entry »
Variable selection using automatic methods
May 22nd, 2010When 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 consuming effort to follow a manual variable selection process. In this case we may consider using automatic subset selection tools to remove some of the burden of the task. Read the rest of this entry »
Linear regression models with robust parameter estimation
May 15th, 2010There 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. Read the rest of this entry »
Analysis of Covariance – Extending Simple Linear Regression
April 28th, 2010The simple linear regression model considers the relationship between two variables and in many cases more information will be available that can be used to extend the model. For example, there might be a categorical variable (sometimes known as a covariate) that can be used to divide the data set to fit a separate linear regression to each of the subsets. We will consider how to handle this extension using one of the data sets available within the R software package. Read the rest of this entry »
Summarising data using box and whisker plots
April 25th, 2010A box and whisker plot is a type of graphical display that can be used to summarise a set of data based on the five number summary of this data. The summary statistics used to create a box and whisker plot are the median of the data, the lower and upper quartiles (25% and 75%) and the minimum and maximum values. Read the rest of this entry »
