sheldon_game <- function(player1, player2){
  alt <- c("rock", "lizard", "spock", "scissors", "paper")
  stopifnot(player1 %in% alt, player2 %in% alt)
  alt1 <- which(alt %in% player1)
  alt2 <- which(alt %in% player2)

  if(any((alt1 + c(1,3)) %% 5 == alt2)) {
    return("Player 1 wins!")
  } else {
    return("Player 2 wins!")
  }
  return("Draw!")
}

Linear algebra in R

Advanced R Programming

Måns Magnusson

Basics in base

Uses LINPACK or LAPACK

Extra functionality : Matrix package

(extra LAPACK functionality)

Linear algebra

Advanced R Programming

Måns Magnusson

# Create matrix
A <- matrix(1:9,ncol=3)

# Block matrices
cbind(A,A)
rbind(A,A)

# Transpose
t(A)

# Addition and subtraction
A + A
A - A

# Matrix multiplication
A%*%A

# Matrix inversion
solve(A)

Linear algebra

Advanced R Programming

Måns Magnusson

# Eigenvalues
eigen(A)

# Determinants
det(A)

# Matrix factorization
svd(A)
qr(A)

# Cholesky decomposition
chol(A)

Advanced R Programming

Måns Magnusson

Let us change our traditional attitude to the construction of programs: Instead of imagining that our main task is to instruct a computer what to do, let us concentrate rather on explaining to humans what we want the computer to do.

- Donald E. Knuth, Literate Programming, 1984

Background

Advanced R Programming

Måns Magnusson

Reproducible research

Literate programming

Dynamic (repeated) reports

(Tutorials)

markdown

Advanced R Programming

Måns Magnusson

simple markup language

alternative to HTML (and LaTeX)

developed further by R-studio 
(see coursepage)

knitr + md = rmd

Advanced R Programming

Måns Magnusson

Add R to markdown

background

Advanced R Programming

Måns Magnusson

popular visualization package

"The grammar of graphics"

- the language of visualization

flexible

examples

the grammar

Advanced R Programming

Måns Magnusson

Three (main) parts:

Create a graph layer by layer

data

geom

aes

The data to visualize (data.frame)

The geometric representation of data

The mapping of colors/shape to data

Store as object (print to plot)

geom

Advanced R Programming

Måns Magnusson

geom_point

Scatterplots

geom_line

Lineplots

geom_boxplot

Boxplot

geom_histogram

Histograms

geom_bar

Barchart

aes

Advanced R Programming

Måns Magnusson

x

y

size

color

shape

aes

Advanced R Programming

Måns Magnusson

geom_point

geom_line

geom_bar

geom

Special

aes

Special

point shape, point size

line type, line size

y min, y max, fill color, outline color

Example

Advanced R Programming

Måns Magnusson

library(ggplot2)

# Preprocessing
data(Nile)
Nile <- as.data.frame(Nile) 
colnames(Nile) <- "level"
Nile$years <- 1871:1970
Nile$period <- "- 1900" 
Nile$period[Nile$years >= 1900] <- "1900 - 1945"
Nile$period[Nile$years > 1945] <- "1945 + " 
Nile$period <- as.factor(Nile$period)

Example

Advanced R Programming

Måns Magnusson

pl <- 
  ggplot(data=Nile) + 
  aes(x=years, y=level) + 
  geom_point()
pl

Example

Advanced R Programming

Måns Magnusson

pl <- 
  ggplot(data=Nile) + 
  aes(x=years, y=level) + 
  geom_line()
pl

Example

Advanced R Programming

Måns Magnusson

pl <- 
  ggplot(data=Nile) + 
  aes(x=years, y=level, color=period) + 
  geom_line(aes(type=period)) + 
  geom_point(aes(shape=period))
pl

Example

Advanced R Programming

Måns Magnusson

pl + theme_bw()

Object orientation

Advanced R Programming

Måns Magnusson

Programming paragdigm

Mutable states

Object orientation

Advanced R Programming

Måns Magnusson

Måns account

currency (12/24) : class variable

current_amount : object variable

no_withdraws : object variable

Fields

Methods

insert()

withdraw()

Object orientation

Advanced R Programming

Måns Magnusson

Savings account

Account

inherits

methods

from

Inheritance

Object orientation in R

Advanced R Programming

Måns Magnusson

S3

Simple

Methods belongs to functions

S3

Advanced R Programming

Måns Magnusson

# Create object
x <- 1:100
class(x) <- "my_numeric"

RC

Advanced R Programming

Måns Magnusson

# Create object with fields and methods
Account <- setRefClass("Account",
  fields = list(balance = "numeric"),
  methods = list(
    withdraw = function(x) {
      balance <<- balance - x
    },
    deposit = function(x) {
      balance <<- balance + x
    }
  )
)

object$copy()