# Posts Tagged ‘ rblogs ’

## Lattice when modeling, ggplot when publishing

October 17, 2011
By

When working in research projects I tend to fit several, sometimes quite a few, alternative models. This model fitting is informed by theoretical considerations (e.g. quantitative genetics, experimental design we used, our understanding of the process under study, etc.) but … Continue reading →

## Linear mixed models in R

October 16, 2011
By

A substantial part of my job has little to do with statistics; nevertheless, a large proportion of the statistical side of things relates to applications of linear mixed models. The bulk of my use of mixed models relates to the … Continue reading →

## Maximum likelihood

October 13, 2011
By
$Maximum likelihood$

This post is one of those ‘explain to myself how things work’ documents, which are not necessarily completely correct but are close enough to facilitate understanding. Background Let’s assume that we are working with a fairly simple linear model, where … Continue reading →

## Simulating data following a given covariance structure

October 12, 2011
By

Every year there is at least a couple of occasions when I have to simulate multivariate data that follow a given covariance matrix. For example, let’s say that we want to create an example of the effect of collinearity when … Continue reading →

## Setting plots side by side

October 11, 2011
By

This is simple example code to display side-by-side lattice plots or ggplot2 plots, using the mtcars dataset that comes with any R installation. We will display a scatterplot of miles per US gallon (mpg) on car weight (wt) next to … Continue reading →

October 10, 2011
By

I tend not to upgrade R very often—running from 6 months to 1 year behind in version numbers—because I had to reinstall all packages: a real pain. A quick search shows that people have managed to come up with good … Continue reading →

## Reading HTML pages in R for text processing

October 10, 2011
By

We were talking with one of my colleagues about doing some text analysis—that, by the way, I have never done before—for which the first issue is to get text in R. Not any text, but files that can be accessed … Continue reading →

## Operating on datasets inside a function

October 9, 2011
By

There are times when we need to write a function that makes changes to a generic data frame that is passed as an argument. Let’s say, for example, that we want to write a function that converts to factor any … Continue reading →

## A brief idea of style

October 8, 2011
By

Once one starts writing more R code the need for consistency increases, as it facilitates managing larger projects and their maintenance. There are several style guides or suggestions for R; for example, Andrew Gelman’s, Hadley Wickham’s, Bioconductor’s and this one. … Continue reading →