This is a flashback post, I was working on species distribution shifts over the last 40 years last summer and recently Rémi Genevest contacted me asking me how I managed to import the CRU TS 1.2 dataset into R. As always a more readable version of the code can be found ... [Read more...]

(Generalized) Linear models make some strong assumptions concerning the data structure: Independance of each data points Correct distribution of the residuals Correct specification of the variance structure Linear relationship between the response and the linear predictor For simple lm 2-4) means that the residuals should be normally distributed, the variance ... [Read more...]

Interaction are the funny interesting part of ecology, the most fun during data analysis is when you try to understand and to derive explanations from the estimated coefficients of your model. However you do need to know what is behind these estimate, there is a mathematical foundation between them that ... [Read more...]

I had a nice workshop two weeks ago in Tübingen (south-germany) concerning Generalized Linear Mixed Models (GLMM) in R. The course was given by two ecologist: Dr. Pius and Fränzi Korner-Nievergelt  that spend now half of their time doing statistical consulting (http://www.oikostat.ch/navigation_engl.htm). ... [Read more...]

R square is a widely used measure of model fitness, in General Linear Models (GLM) it can be interpreted as the percent of variance in the response variable explained by the model. This measure is unitless which makes it useful to compare model between studies in meta-analysis analysis. Generalized Linear ... [Read more...]

A friend of mine told me that she was spending her day colouring R plot because she never understood how to put color in them. This triggered a nerdy reaction in me that I had to put in a basic function. This was actually a funny exercise for two reasons: ... [Read more...]

I am currently following a course on probability theory in coursera (https://www.coursera.org/course/probas) and I’ve seen some graphs concerning the outcome of some dice throws. Being an R-nerd I wrote a little function to do this in R. This is nothing fancy just I find ... [Read more...]

You are one click away from a post on the various way one can change the legend title in ggplot2, combine several aesthetic, remove the legend in ggplot2. http://rpubs.com/hughes/10012Filed under: R and Stat Tagged: ggplot2, R [Read more...]

Here is the link to the article: http://rpubs.com/hughes/7812 There you will discover how to simulate and fit: power function, Michaelis-Menten equation and sigmoid curves in R, the fit is done by least-square using the ‘nls’ function.Filed under: R and Stat Tagged: NLS, R [Read more...]

In classical linear modelling we are assuming that the response variable (Y) is normally distributed, however for certain type of data like count data or presence/absence data this is not the case. There is in statistic an ensemble of technique called Generalized Linear Modelling (GLM in short) where the ... [Read more...]

Here is a post with some information to control the layout of your graph produced by the ggplot library: http://rpubs.com/Lionel/6557 Enjoy!Filed under: R and Stat Tagged: ggplot, R [Read more...]

Here is a post discussing the possibilities of the rasterVis package: http://rpubs.com/Lionel/6374Filed under: R and Stat Tagged: R, raster [Read more...]