It used to be that the one of the first decisions to make when learning to program was between compiled (e.g. C or FORTRAN) and interpreted (e.g. Python) languages. In my opinion these days one would have to be a … Continue reading →
It used to be that the one of the first decisions to make when learning to program was between compiled (e.g. C or FORTRAN) and interpreted (e.g. Python) languages. In my opinion these days one would have to be a … Continue reading →
Another R tip: beware of as.character applied to a list. Really, beware of grep with a list: You might have thought that the result would be just 1, but grep expects a vector of character strings. If the input is not that, it uses as.character(). Since the result of that starts with "c(", grep finds […]
It’s widely understood that, in R programming, one should avoid for loops and always try to use apply-type functions. But this isn’t entirely true. It may have been true for Splus, back in the day: As I recall, that had to do with the entire environment from each iteration being retained in memory. Here’s a […]
![x[[c(5,3)]]](http://feeds.wordpress.com/1.0/comments/kbroman.wordpress.com/1600/)
An R tip: Did you know that x[[c(5,3)]] is the same as x[[5]][[3]]? I should make more thorough use of this. In the help file for [[: [[ can be applied recursively to lists, so that if the single index i is a vector of length p, alist[[i]] is equivalent to alist[[i1]]...[[ip]] providing all but […]
Many of the posts in this blog have been concerned with using MCMC based methods for Bayesian inference. These methods are typically “exact” in the sense that they have the exact posterior distribution of interest as their target equilibrium distribution, but are obviously “approximate”, in that for any finite amount of computing time, we can […]
Rainer pointed out, in response to my post, Row names in data frames: Beware of 1:nrow, that if I’d used rownames(x) <- as.character(1:3) rather than rownames(x) <- 1:3, I wouldn’t have had the problem I’d seen. If you type rownames(x) you see the same result as rownames(z), and is.character(rownames(x)) and is.character(rownames(z)) both return TRUE, but […]
I spent some time puzzling over row names in data frames in R this morning. It seems that if you make the row names for a data frame, x, as 1:nrow(x), R will act as if you’d not assigned row names, and the names might get changed when you do rbind. Here’s an illustration: As […]
We don’t get many kids seeking candy at our house. I’m not sure if there just aren’t many kids in the neighborhood, or if it’s our location (next to the pond, with a big gap before the next house). I decided to keep track. As usual, we bought a huge bag of candy, and we […]
One of the coolest R packages I heard about at the useR! Conference: Toby Dylan Hocking‘s directlabels package for putting labels directly next to the relevant curves or point clouds in a figure. I think I first learned about this idea from Andrew Gelman: that a separate legend requires a lot of back-and-forth glances, so [...]
Let’s start this blog off right, with the stupidest R mistake I’ve ever made (I think). In the R package that I write, R/qtl, one of the main file formats is a comma-delimited file, where the blank cells in the second row are important, as they distinguish the initial phenotype columns from the genetic marker [...]
