R is `GNU S', a freely available language and environment for statistical computing and graphics which provides a wide variety of statistical and graphical techniques: linear and nonlinear modelling, statistical tests, time series analysis, classification, clustering, etc. R is distributed by the Comprehensive R Archive Network (CRAN). R may be downloaded and installed for your hardware from this site.
What you need to do to get started
USGS R package developed to directly ingest USGS data into R
Examples of functionality I find useful in R.
Perform arithmetic.
> 3*(4+7.3)
[1] 33.9
Assign and work with variables
> g=9.81
> m=30
> f=m*g
> f
[1] 294.3
Combine values into a vector
> a=c(1,2,3,4)
> b=a*2
> b
[1] 2 4 6 8
> ls() # list the objects in your workspace
> rm(f,m,a,b) # Remove objects (to clean up)
> setwd('d:/') # Set working directory - note forward slash
Read a data file. The file boise.txt has
been formatted as follows
1911 10 398
1911 11 395
1911 12 398
1912 1 507
1912 2 421
1912 3 530
...
comprising columns giving the year, month and flow. It is read
as follows
> tt=matrix(scan("boise.txt"),ncol=3,byrow=T)
Read 3276 items
> yr=tt[,1] # put year, month and flow columns in separate
vectors
> mo=tt[,2]
> flow=tt[,3]
> ym=yr+mo/12 # a plotting index in fraction of years
> plot(ym,flow,type="l")
Built in functions
> mean(flow)
[1] 1208.674
> var(flow)
[1] 1800607
Make your own function
sdev=function(x)
{
y=var(x)
return(sqrt(y))
}
Use it
> sdev(flow)
[1] 1341.867
Demonstrate graphics capability
demo(graphics)
Use a package
Packages/Load Package ... select ts (time series)
acf(flow) # autocorrelation function