# R code for lecture 1

log2(32)

sqrt(2)

seq(0, 5, length = 6)

plot(sin(seq(0,  2*pi,  length = 100) ) )

history()

scal<-6

value<-7

whales<-c(74,122,235,111,292,111,211,133,16,79)

simpsons<-c("Homer", "Marge", "Bart", "Lisa", "Maggie")

sum(whales)

length(whales)

mean(whales)

sort(whales)

var(whales)

max(whales)

help(mean) 

? mean()

help.search('sin()') 

1:10

rev(1:10)

10:1

a=1; h=4; n=5

a+h*(0:(n-1))

rep(1,10)

rep(1:3,3)

mat<-matrix(0,2,3)

mat2<-rbind(c(71,172),c(73,169),c(69,160),c(65,130))

mat3<-cbind(c(71,73,69,65),c(172,169,160,130))

mat4<-matrix(1:10,2,5, byrow=T)

whales<-c(74,122,235,111,292,111,211,133,16,79)

whales[2]

whales[1:4]

whales[-1]

whales[whales>100]

which(whales>100)




mat2<-rbind(c(71,172),c(73,169),c(69,160),c(65,130))

mat2[,2]

mat2[2,]

mat2[1:3,1]

mat2[c(2,4),]

mat2[-c(2,4),]




X=1:5

X<5; X>1 

X >1 & X <5; X >1 | X <5
X >1 && X <5; X >1 || X <5


x[is.na(x)]<-0
  
mean(x, na.rm=TRUE)

ls()

getwd()
setwd("C:/Documents and Settings/wguo/My Documents")

save.image(file="xx.RData")
load(file="xx.RData")


gpa=scan(file="gpa.txt")
gpa=read.table(file="gpa.txt", header=FALSE)
read.table(file=url("http://www.math.csi.cuny.edu/UsingR/Data/whale.txt"),header=T)



range(lynx) #lynx is a built-in dataset
library(MASS) # load a library
data(survey)

library(MASS); data(Sitka)
names(Sitka); length(Sitka$tree) 

attach(Sitka); summary(tree)
detach(Sitka)