R - tutorial 1


###  All data are stored locally in the directory where R-was started, unless it is not specified.
###  Data are accessed by typing the name of the variable
###  All functions are called by using parentheses 
###  Array elements are addressed by using brackets
###  strings are enclosed in quotes (either single or double)

ls()
help(ls)
save(file="R_mystuff")
history()
help.start()


###  comments in R are preceded by a pound sign #

###  to execute a file with R-functions or commands:
source("file_name")

###  setting scalar values:

###  is a comment line

a = 25
a <- 25
b = 23

c = a*b

vectors 

x = 1:25
x = seq(34, 92, by=3)

###   concatenation:
x = c(1:12, 34:65)
y = 34:65

##  or:
z = c(x, y)



###  multiply x by a scalar a
x*a

###  matrices

### cbind, rbind

x = matrix(1:100, byrow=T, nrow=10)

### transpose:

t(x)

###  Accessing parts of a matrix
x[,2]
x[2,]
### submatrix:
x[2:5,6:9]

### Functions: built in math
### sin(x)  cos(x), exp(x), log(x), etc....

### matrix multiplication

x = matrix(1:6, 2, 3)
y = 1:3
x %*% y

### This is NOT equal to x *y

### Reading a file

X = scan(file="name_of_file")


###  Z:/glees/data/GRAB/GEOL520/Data_Files

X = scan(file="https://blackboard.unc.edu/courses/1/GEOL152.001.SPRING2005/content/_1357982_1/S1.res")
X = scan(file="Z:/glees/data/GRAB/GEOL520/Data_Files/S1.res")


X = scan(file="C:/Documents and Settings/lees/Desktop/S1.res")

X = scan(file="Z:/glees/data/GRAB/GEOL520/Data_Files/xy.dat", list(x=0, y=0))

###  Structures

### structures in R are accessed through component names  or indicies
###  for example:
X[[1]]

X$x


###  PLOTTING


plot(X$x, X$y)
##  add a title


plot(X$x, X$y, type="n")
points(X$x, X$y, pch=3)
title(main="This is a wierd plot")


####  make a plot but do not add data, omit the axis names


x = rnorm(100)
y = runif(100)

X = list(x=x, y=y)


plot(X$x, X$y, type="n", xlab='', ylab='')
points(X$x, X$y, pch=3)
title(main="This is a wierd plot")
title(xlab="time,s", ylab="amplitude, N")

####  make a plot but do not add data, omit the axis names


plot(X$x, X$y, type="n", xlab='', ylab='', axes=FALSE)
###  this created the plot and now we have to add to it
points(X$x, X$y, pch=6)



title(main="This is a wierd plot")
title(xlab="time,s", ylab="amplitude, N")

axis(1)

axis(4)

axis(2, at=seq(from=min(X$y), to=max(X$y), by=diff(range(X$y))/10    )  )

###  add in subtick marks
axis(1, at=seq(from=min(X$x), to=max(X$x), by=.05), labels=FALSE, tck=0.005)

axis(3, at=seq(from=min(X$x), to=max(X$x), by=.1),  tck=-0.005)


box()


#################

#########  finding things on the plot:

####  two  main functions locator and identify

locator(1)

L = locator(5)

L

points(L$x, L$y, pch=2, col=3)

###  for infinite number of points:

L = locator()

############   click stop to end input

L = locator(type="p", pch=8, col="blue")

###########################################

I = identify(X$x, X$y)

I

points(X$x[I], X$y[I], col="purple", pch=1, cex=2)


###############


plot(X$x, X$y, type="n", xlab='', ylab='')
points(X$x, X$y, pch=3)
title(main="This is a wierd plot")
title(xlab="time,s", ylab="amplitude, N")


symsize = rep(diff(range(X$x))/10, length(X$x[I]))

symbols(X$x[I], X$y[I], circles=symsize, fg="purple",  inches=FALSE, add=TRUE)

symbols(X$x[I], X$y[I], circles=symsize, fg="purple", bg="green" , inches=FALSE, add=TRUE)

###############


plot(X$x, X$y, type="n", xlab='', ylab='')
points(X$x, X$y, pch=3)
title(main="This is a wierd plot")
title(xlab="time,s", ylab="amplitude, N")


symsize = abs(rnorm(length(X$x[I]), mean=.1, sd=.03))


symbols(X$x[I], X$y[I], circles=symsize, fg="purple", bg="green" , inches=FALSE, add=TRUE)


###############  distributions and probability

###  empirical distribution of x

par(mfrow=c(1,2))

hist(x)
hist(y)

par(mfrow=c(2,1))

hist(x)
hist(y)

###############

##  what is the probability of getting .2 or less in y?

##  need to count all the points, need to count points less or equal to .2
###   take the ratio....

N = length(y)
n = length(y[y<=0.2])

rat = n/N

####  rat is about 12%


####  source a file with R commands

source("d:/LEES/CLASSES/GEOL_520 Data_Analysis/LAB_NOTES/RsourceTest.txt")


#######################


###  functions

##  create a function to get the dot product of two vectors

dot<-function(x,y)
{
	A = x*y
	B = sum(A)
	return(B)
}