28 Feb 2012

Apprentice Piece with Lattice Graphs

Lattice graphs can be quite tedious to learn. I don't use them too often and  when I need them I usually have to dig deep into the archives for details on the parameter details.
The here presented example may serve as a welcome template for the usage of panel functions, panel ordering, for drawing of lattice keys, etc.
You can download the example data HERE.

(Also, check this resource with examples by the lattice-author). 

27 Feb 2012

Testing the Effect of a Factor within each Level of another Factor with R-Package {contrast}

This is a small example of how custom contrasts can easily be applied with the contrast-package. The package-manual has several useful explanations and the below example was actually grabbed from there.
This example can also be applied to a GLM but I choose to use a LM because the coefficients are more easily interpreted.

1 Feb 2012

Transformation of Several Variables in a Dataframe

This is how I transform several columns of a dataframe, i.e., with count-data into binary coded data (this would apply also for any other conversion..).

count1 <- count2 <- count3 <- count4 <- sample(c(rep(0, 10), 1:10))
some <- LETTERS[1:20]  
thing <- letters[1:20]  
mydf <- data.frame(count1, count2, count3, count4, some, thing)

ids <- grep("count", names(mydf))
myfun <- function(x) {ifelse(x > 0, 1, 0)}
mydf[, ids] <- lapply(mydf[, ids], myfun)

p.s.: Let me know if you know of a slicker way.