The Seasonal Trend Decomposition using Loess (STL) is an algorithm that was developed to help to divide up a time series into three components namely: the trend, seasonality and remainder. The methodology was presented by Robert Cleveland, William Cleveland, Jean McRae and Irma Terpenning in the Journal of Official Statistics in 1990. The STL is available within R via the stl function. Read the rest of this entry »
Seasonal Trend Decomposition in R
January 11th, 2013Graph Types: Pie Charts
October 13th, 2012The pie chart is a frequently seen graph that uses area to compare percentages for a set of categories. Although this type of graph is based on comparing single metric for each category the display is two dimensional but sometimes even appears in three dimensions. Read the rest of this entry »
Data from the ONS
September 15th, 2012The Office for National Statistics (ONS) in the UK makes various data sets publicly available on their website. This includes a number of time series that could be useful for learning about different statistical models for time series data.
Linear Algebra Video Tutorials
August 19th, 2012The following website has some interesting introductory course videos on linear algebra from Gilbert Strang at MIT.
R Graphical Manual
July 5th, 2012The R Graphical Manual is worth checking out for ideas about graphing data.
Graph Design Principles
June 25th, 2012There are a set of basic principles that hold true for the design of many graphs and various authors have their own preferences. One author who is prominent due to his good work in the area of data visualisation and presentation of evidence to support decision making is Edward Tufte. Read the rest of this entry »
Logistic Regression and Bias Reduction
May 22nd, 2012David Firth published a paper in 1993 on maximum likelihood estimation and the reduction of bias when using this approach. The research in this area appears to provide benefit for logistic regression in small data sets where there is complete of quasi separation. This approach has been implemented for Generalized Linear Models in the brglm package. Read the rest of this entry »
Theme Elements in ggplot2
May 3rd, 2012Melt
April 5th, 2012There are many situations where data is presented in a format that is not ready to dive straight to exploratory data analysis or to use a desired statistical method. The reshape2 package for R provides useful functionality to avoid having to hack data around in a spreadsheet prior to import into R. Read the rest of this entry »
Tikz Paths and Decorations
March 17th, 2012The tikz drawing system can be used to draw basic solid black lines and simple shapes which can reasonably easily be adjusted to allow alternative patterns and decorations. Read the rest of this entry »
