Just read about a new R package called alphahull (paper) that sounds like it might be a good candidate for addressing this request regarding concave hulls. Below are some notes on computing alpha-shapes and alpha-hulls from spatial data and converting the results returned by ashape() and ahull() into SP-class objects. Note that the functions...
Confidence intervals and prediction intervals are used by statisticians on a regular basis. Another useful interval is the tolerance interval that describes the range of values for a distribution with confidence limits calculated to a particular percentile of the distribution. The R package tolerance can be used to create a variety of tolerance intervals of
Missing Data
Soil scientists routinely sample, characterize, and summarize patterns in soil properties in space, with depth, and through time. Invariably, some samples will be lost or sufficient funds required for complete characterization can run out. In these cases the scientist is left with a data table that contains holes (so to speak) in the rows/columns that are...
R can be annoying in that even if you stretch your terminal or R GUI session to a whole screen width it will still only show 80 characters width. This can make wide tables really hard to read. options(width=150)Use the options command width to set...
R can be annoying in that even if you stretch your terminal or R GUI session to a whole screen width it will still only show 80 characters width. This can make wide tables really hard to read. options(width=150)Use the options command width to set...
For interactive data analysis, the default fonts used by SAS and R are acceptable, if not beautiful. However, for publication, it may be important to manipulate the fonts. For example, it would be desirable for the fonts in legends, axis labels, or o...
Here’s the situation. Web applications, built using a framework (e.g. Rails, Django) are great for fetching data from a database and rendering it. They’re not so great for crunching and charting the data. Conversely, R is great for crunching and charting, but doesn’t make for a great web application. The idea then, is to let 
I just got back from R/Finance 2010 in Chicago. If you couldn't make it this year, I strongly encourage you to attend next year. I will post a more comprehensive review of the event in the next couple days, but I wanted to share some of my notes spec...
Darren Wraith pointed out this column about sudokus to me. It analyses the paper by Newton and De Salvo published in the Proceedings of the Royal Academy of Sciences A that I cannot access from home. The discussion contains this absurd sentence “Sudoku matrices are actually more random than randomly-generated matrices” which shows how mistreated 
A scatter plot is a graph used to investigate the relationship between two variables in a data set. The x and y axes are used for the values of the two variables and a symbol on the graph represents the combination for each pair of values in the data set. This type of graph is
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
