Working with Probability Distributions

May 31st, 2009

Probability distributions have a central role in Statistics and the R software has functions to work with a large range of distributions – the syntax has been selected to provide some consistency based on the type of information required about a distribution. Read the rest of this entry »

Sequences and Other Regular Arrangements of Data

May 26th, 2009

In Statistical analysis there are frequently situations where regular structures occur, such as in designed experiments, and R has facilities for generating data frames in a simple way. Read the rest of this entry »

Vector Calculations to avoid Explicit Loops

May 23rd, 2009

The S programming language has facilities for applying a function to all the individual elements of a vector, matrix or data frame which avoid the need to make explicit use of loops. In fact using loops in R is not recommended as this will slow down the calculations, but there will of course be some situations where it is unavoidable. Read the rest of this entry »

Transformations to Create New Variables

May 18th, 2009

There are many situations where we might be interested in creating a new variable by transforming one of the variables already in the data frame. The R programming language can be used for either simple transformations or more complicated mathematical expressions where necessary. Read the rest of this entry »

Cross-tabulation of Data

May 15th, 2009

The contingency table is used to summarise data when there are factors in the data set and we are interested in counting the number of occurrences of each combination of factor variables. In R there are different ways that these types of table can be produced and manipulated as required. Read the rest of this entry »

Producing Data Summaries

May 11th, 2009

The first stage of most investigations is to produce summaries of the data to identify any unusual records and to get a overall feel for the contents of the data. This initial data analysis usually involves tabulation and plotting of data and there are a variety of functions available in R to generate the required summaries of interest. Read the rest of this entry »

Working with Subsets of Data

May 8th, 2009

There are often situations where we might be interested in a subset of our complete data and there are simple mechanisms for viewing and editing particular subsets of a data frame or other objects in R. Read the rest of this entry »

Importing Data from other Statistical Software Packages

May 1st, 2009

There are a large of number of software packages that are available for data analysts and the foreign package in R has functions defined to read data from some of the most commonly used packages that have their own proprietary data format. For other packages the user can often export data to a delimited text file which can then be handled easily by R. Read the rest of this entry »