##### R tips
##### updated on 01/19/2011

### R tips No. 1: how to use R helps?
# want to know how to use function "runif"
?runif
# want to know how to generate random numbers from normal distribution
help.search("normal distribution")
?Normal

### R tips No. 2: how to print or save R graphs?
# if use menu operations: [1] click the R graph window; 
#                         [2] (menu)File --> print or File --> Save as
# if use R command lines: for example, to save the graph into a file "normal.ps"
x <- rnorm(1000, mean=1, sd=2)
postscript("normal.ps",paper="special",width=8,height=7,horizontal=F)
par(mfrow=c(1,1))
hist(x, freq=F)
curve(dnorm(x, mean=1, sd=2), lwd=2, lty=2, add=T)
dev.off()

## R tips No. 3: how to count the computation time (in seconds)
tempt <- proc.time()
temp <- runif(10000000)
proc.time()-tempt

## R tips No. 4: generating random numbers from distributions of standard parameter families
## available R functions
# rbeta -- The Beta Distribution 
# rbinom -- The Binomial Distribution 
# rcauchy -- The Cauchy Distribution 
# rchisq -- The (non-central) Chi-Squared Distribution 
# rexp -- The Exponential Distribution 
# rf -- The F Distribution 
# rgamma -- The Gamma Distribution 
# rgeom -- The Geometric Distribution 
# rhyper -- The Hypergeometric Distribution 
# rlnorm -- The Log Normal Distribution 
# rlogis -- The Logistic Distribution 
# rmultinom -- The Multinomial Distribution 
# rnbinom -- The Negative Binomial Distribution 
# rnorm -- The Normal Distribution 
# rpois -- The Poisson Distribution 
# rsignrank -- Distribution of the Wilcoxon Signed Rank Statistic 
# rt -- The Student t Distribution 
# runif -- The Uniform Distribution 
# rweibull -- The Weibull Distribution 
# rwilcox -- Distribution of the Wilcoxon Rank Sum Statistic