R help

Exploratory data analysis

Finding out n, distribution

library(psych)
cols <- c("n", "mean", "median", "min", "max", "sd")
desc <- data.frame(describe(dt))[cols]

More info see here and here.

Reliably importing packages

packages <- c("xtable", "stats", "plyr", "dplyr", "ggplot2", "RColorBrewer")

for(i in 1:length(packages)) {
	pkg <- packages[i]
	if (!require(pkg, character.only=TRUE)) {
		install.packages(pkg, repos="http://cran.rstudio.com/")
		library(pkg, character.only=TRUE)
	}
}

Misc

Likelihood ratio test

# Likelihood of both models, degrees of freedom
# https://onlinecourses.science.psu.edu/stat504/node/220
p_interaction <- function(lik1, lik2, df){
  d = abs(lik1-lik2);
  return (dchisq(d, df));
}
p_interaction(5521.201, 5504.008, 8);