Monthly Archives: August 2006


Niche business becoming a commodity. 11

Niche products, niche businesses, niche markets — small businesses are often qualified as surviving in niches, finding their niche, defining or redefining their niche. Most people think entrepreneurs start their own business, but most buy running ventures, like franchises, already in surviving niches. Steps to understanding and predicting quantitative business niches are in early stages. […]


How are bimodal distributions created and modeled? 22

Demetris Koutsoyiannis responds: I agree that a bimodal distribution is seldom seen. Well, my experience is not from ecological but mainly from hydrological processes but I suspect that the behaviours would be similar. I have seen claims of bimodality several times but I was never convinced about them as I did not read any argument […]


What are the conditions for valid extrapolation of statistical predictions? Answer II. 21

Demetris Koutsoyiannis Before I attempt to describe my answer, I would like to do some clarifications on the nature of a statistical prediction and mention some points than need caution. 1. A statistical prediction should be distinguished from a deterministic prediction. In a deterministic prediction some deterministic dynamics of the form y = f(x1, …, […]


How to regress a stationary variable on a non stationary variable? Answer II 41

Demetris Koutsoyiannis responds: I think that such questions should not be treated in an algorithmic manner and that it is important to formulate them in the clearest and most consistent manner. So, let us assume that we have a nonstationary stochastic process X(t) and a stationary process Y(t); I have interpreted here “variable” as process […]


How to regress a stationary variable on a non stationary variable? Answer I 9

Martin Ringo responds: This is the wrong question. The analyst shouldn’t be worried about whether the dependent or independent is stationary or non-stationary. The issue is the error term. In the Box-Jenkins procedure(s) — or maybe I should call it paradigm — the non-stationary stuff is removed. To me that removal is what is interesting, […]


Comparison of Climate Variables in Species Models 10

One of the main inputs into a niche model is the environmental variables. Optimizing the choice of variables is important for many reasons, primarily interpretation and subsequent accuracy on independent test data. In almost all cases to date, annual climate averages have been used in modeling species distributions. Where models have been developed and annual […]


Three Variable Bayes Net for Species Prediction 3

The post Bayesian Networks introduced this useful and flexible form of modeling. Here is an example of a Bayesian Belief Net or BBN model of a simple three variable species prediction system. In Fig 1 the top node is habitat quality for the species. Two lower nodes, the average temperature (Av_Temp) and the vegetation (Veg_Type) […]


R Sweave Example 13

The previous post “Writing a Book Using R” described using latex for writing a book, saving time with one master bibliography and other organizational devices. Sweave allows R code to be included in a latex file. This is a good marriage; while latex provides typeset text; R is statistically and graphic oriented. Here is an […]


Hurst Coefficient Software 13

Long-range dependence is being identified many disciplines such as, networking, databases, economics, climate and biodiversity. LTP is competing with the sexy “long tail” for top spot as a theory of cultural consumption. Thus, the need for software offering complete long-range dependence analysis is crucial. While there are some steps towards this direction, none are yet […]


Rolin Jones Discovers Clark Glymour 5

A number of posts here and here have compared the “hockey stick” construction of past temperatures to the play by Rolin Jones to illustrate an area of science where dramatization and self-promotion have become confused with the search for scientific truth. The background of this story is fascinating. In a story on the playwright at […]


R code in Econometrics 4

One of the best, and possibly the only, guide to advanced use of R is the manual “Econometrics in R” by Grant V. Farnsworth. Dated June 26, 2006 it was originally written as part of a teaching assistantship and personal reference. Some of the topics covered I have found nowhere else. The manual is particularly […]


Is Temperature a Random Walk? 35

We use the data from CRU, and input it into R using the code in the post R Code to Read CRU Data. The initial approach to testing whether global temperatures from CRU is to run a Dickey-Fuller Test for Unit Root. The augmented Dickey-Fuller test checks whether a series has a unit root. The […]


R Code for Brownian Motion 23

According to Wikipedia the mathematical model for Brownian motion (also known as random walks) can also be used to describe many phenomena as well as the random movements of minute particles, such as stock market fluctuations and the evolution of physical characteristics in the fossil record. The simple form of the mathematical model for Brownian […]


R Code to Read CRU Data 14

Reading CRU data is an opportunity to demonstrate some of the features available for programming in R. The Climate Research Unit (CRU) data is a record of the global, northern and southern hemisphere temperatures compiled from temperature sources around the globe for the last 150 years. The files are located at http://www.cru.uea.ac.uk:80/cru/data/temperature/ and look like […]


A Simply Told Ptolemaic 10

The Washington Post has finally commented on the Wegman Report, and Whitfield hearings I and II on the so-called “hockey stick” graph — a trend line that purports to show little temperature variation throughout the Medieval Warm Period and a sudden and dramatic increase in global temperatures in the 1990s and therefore looks like a […]


Simple Linear Regression Models 32

A “simple” regression model is simple because it has a single independent variable instead of multiple independent variables. Because simple is in the name, many people make the mistake of thinking they are simple to use. One mistake is to first apply them to their data, without checking to see if the assumptions are met. […]


Intelligent Emotions 4

Emotional Intelligence or EI is a concept popularized by Daniel Goleman as a complement to competence measures like IQ in the emotional sphere. But EI has the problem that it is not quantitatively defined with a number and standards like IQ. So it has been criticized by people like Eysenck: “exemplifies more clearly than most […]


How to Predict Random Numbers 20

The previous post “Random Numbers Predict Future Temperatures” used random numbers for prediction of climate. Random numbers may also be predicted. This is a major difference between models and natural phenomena. Random numbers generated by computer can always be predicted exactly given knowledge of the code, and so have a deterministic generating mechanism, or model. […]


Niche Media 37

If a picture is worth a thousand words, a video is worth more. The use of compelling media has been undergoing something of a revolution recently, driven by new social sites like YouTube. I like Salsa music, and found this clip of the Colombian band Guayacan (I think I saw these guys in Mexico City […]