# To enter Splus type 
  Splus	
# You could add the option -e to add command editing

# 1. We study operators:
#	 + , - , * , /
#	%/%  integer divide 
#	%%   modulus operator
#	^    Exponentiation 
#	-    unary minus
#    Precedence   ^ * / + -
  7 %% 3 + 4%/% 3
  7 %% 3^2
# Sequence operator
  1:5
  27:3
  1:5 + 1:5 # vector arithmetic	
  1:5 + 3   # precedence
  2^(1:5)
# c function combines vectors
  c(1,2*4,4, 10:12)
  c("dog","cat","mouse")
# Exercise 1: Produce the sequence
# 2 3 4 5 1 2 3 5 1 2 3 4 5...
# Exercise 2: Produce the vector
# "Monday", "Tuesday", "Wednessday"
##### The assignment operator '<-' #####
  primes <- c(1,2,3,5,7,11) 
  greeting <- "Hello World"
# S data Objects are saved in .Data
# Data in S are of mode: logical,integer
# real ,  character.
# Common S functions:abs, cos, exp,log, 
# log10, round, sin, sqrt
# len, max,mean,median, min,prod,sum,var
# range, sample, sort, seq, runif,rnorm
### Random numbers ####
  runif(10)
  x <- rnorm(10)
# Ex compute s-dev of x
  sqrt(var(x))

# function seq
  seq( len=12, to=27, by=2)

# to stop a computation ^C

# to get help 
  help(median) 
# or use the ? character:
  ?median

# options
  options(width=132,length=200)

# create a file with a data set in your favourite editor. I use emacs
# could be an array of numbers 6 by 4 separated by spaces 
  !emacs myfile
  !cat myfile
# creating datasets
  x <- scan()
  y <- scan("myfile")
# creating data frames
  y <- read.table("myfile")
# my data objects
  ls()  
  objects(pat="x")
# Important to remove unused
  rm(x) 
  x <- sin(y)
###  Graphics #####
#  Devices: printer(), tek4014(), X11(), postscript()
  printer(80,28)
  par(mar=c(2.2,2.2,1,1))
  plot(y)    #simple scatter plot
  plot(y,type="l")     #connected lines
# log-log plot
  x <- y$V1
  y <- y$V2
  plot(x,y,log="xy")
  show()
# do not plot, then
# use text to label each point from 1 to n
  plot(x,y,type="n");text(x,y,seq(x))   
# Using a better device:
  X11()
  plot(corn.rain,corn.yield)
  abline(20,1) # addline y = a+b x. Pick the values of a and b yourself
  abline(h=30); abline(v=12)
  title(sub="This is corn data")
#  Sending a graph to a postscript file
  postscript()
  plot(corn.rain,corn.yield)
  title(sub="This is corn data")
  graphics.off()
#####Matrices#####
  x <- matrix(scan("myfile"),3,4,byrow=T) 
  x <- matrix(sqrt(1:12),4,3)-3
  x
  x[ 3,1:2]
  rownum <- 1:4  # get odd rows
  rownum %% 2 
  x[rownum %%2 ==1 , ]
  x[ -1,-c(1,3)]
  nrow(x)
  ncol(x)
  y <- 1:3
  x%*%y
  y <-  rnorm(4)
  solve(t(x) %*% x) %*% (t(x) %*% y)
  x <- matrix(rnorm(18),6,3)
  y <-  x%*% c(1,2,3) + rnorm(6)/4
  solve(t(x) %*% x) %*% (t(x) %*% y)
  lsfit(x,y,int=F)
############ Data Structures#####
  simple <- list(name= "Simple Stats",
                 mean= mean(x),sdev=sqrt(var(c(x))))
  simple$name
##Create a copy of "myfile" with variable names in the first row.
!emacs myfile
  x <- read.table("myfile1")
  names(x)
  x$z <- x$x + x$y -3
  names(x)
##### LOGICAL OPERATORS #######
# >  , >= , < , <= , == , != , & , | or ! Not
u <- x > 0
u
print(!u)
x[u]
u <- log(x)
is.na(u)
u$z[is.na(u$z)] <- 0
#  You can put some or all these instructions into your own file "program"
#  and excecute them all at once with the instruction:
#           source("program")
########## CONDITIONAL #########
u <- sum(x)
if( u < 0) {  x <-  -x  }
######### LOOPS ############
z <- matrix(rnorm(200),20,10)
mean.samp <- NULL
for(i in 1:10) {
          mean.samp[i] <- mean(z[,i])
}
stem(mean.samp)
############# FUNCTIONS ########
fourmom <- function(x) {
        m1 <- c(mean(x))
        m2 <- mean(x^2)
        m3 <- mean(x^3)
        m4 <- mean(x^4)
        list(m1=m1,m2=m2,m3=m3,m4=m4)
}
fourmom(x)