10 R One Liners to Impress Your Friends

http://datadebrief.blogspot.com/2011/06/10-r-one-liners-to-impress-your-friends.html


Multiply Each Item in a List by 2

#lists lapply(list(1:4),function(n){n*2}) # otherwise (1:4)*2

Sum a List of Numbers

#lists lapply(list(1:4),sum)   # otherwise sum(unlist(list(1:4))) # or simply sum(1:4)

Verify if Exists in a String

wordlist = c("lambda", "data", "plot", "statistics", "R") tweet = c("R is an integrated suite of software facilities for data manipulation, calculation and graphical display") wordlist[wordlist %in% (c(unlist(strsplit(tweet,' ', fixed=T))))]

Read in a File

readLines("data.file", n=-1)

Happy Birthday to You!

lapply((1:4),function(x){ paste(c("Happy Birthday to ", ifelse(x!=3, "you", "dearName")), sep="", collapse="")})

Filter list of numbers

n = c(49, 58, 76, 82, 88, 90); c(list(n[which(n<=60)]),list(n[which(n>60)]))

Fetch and Parse an XML web service

 

library('XML'); xmlParseDoc('http://search.twitter.com/search.atom?&q=R-Project', asText=F)

Find minimum (or maximum) in a List

# for lists  lapply(list(c(14, 35, -7, 46, 98)), min, classes="numeric", how="replace") # otherwise min(unlist(list(14, 35, -7, 46, 98)))# or simply min(c(14, 35, -7, 46, 98)) max(c(14, 35, -7, 46, 98))

Parallel Processing

# http://cran.r-project.org/web/packages/doSMP/vignettes/gettingstartedSMP.pdf # copy from Section 4 An example doSMP session library(doSMP); w <- startWorkers(workerCount = 4); registerDoSMP(w); foreach(i = 1:3) %dopar% sqrt(i)

Sieve of Eratosthenes

##ok, this one is a little cheating library('spuRs'); primesieve(c(),2:50)