Creating a Stratified Random Sample of a Dataframe
[This article was first published on theBioBucket*, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Expanding on a question on Stack Overflow I’ll show how to make a stratified random sample of a certain size: Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
d <- expand.grid(id = 1:35000, stratum = letters[1:10])
p = 0.1
dsample <- data.frame()
system.time(
for(i in levels(d$stratum)) {
dsub <- subset(d, d$stratum == i)
B = ceiling(nrow(dsub) * p)
dsub <- dsub[sample(1:nrow(dsub), B), ]
dsample <- rbind(dsample, dsub)
}
)
# size per stratum in resulting df is 10 % of original size:
table(dsample$stratum)
To leave a comment for the author, please follow the link and comment on their blog: theBioBucket*.
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.