?exp # opens documentation for 'exp' function
??exponential # searches documentation for "exponential"

Vectors and Matrices

Create vectors with c function:

s <- c(1, 2, 3, 4)
s

## [1] 1 2 3 4

Create matrices with matrix function:

A <- matrix(1:9, nrow = 3, ncol = 3)
B <- matrix(c(1, 2, 2, 3, 4, 5), nrow = 2)
print(A)

##      [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9

print(B)

##      [,1] [,2] [,3]
## [1,]    1    2    4
## [2,]    2    3    5

Use cbind and rbind to combine vectors and matrices:

a <- cbind(1:3, 6:8)
print(a)

##      [,1] [,2]
## [1,]    1    6
## [2,]    2    7
## [3,]    3    8

C <- rbind(A, B)
print(C)

##      [,1] [,2] [,3]
## [1,]    1    4    7
## [2,]    2    5    8
## [3,]    3    6    9
## [4,]    1    2    4
## [5,]    2    3    5

Generate random data

Generate random data from the normal distribution with rnorm function:

x <- rnorm(100, mean = 5, sd = 2)
mean <- mean(x)
std <- sd(x)
head(x)

## [1] 4.900988 4.940206 3.258242 5.483131 2.901180 6.743156

print(paste("Mean:", mean))

## [1] "Mean: 5.28215373900054"

print(paste("Standard deviation:", std))

## [1] "Standard deviation: 2.18814066784594"

Loading Libraries

Install packages with install.packages function:

install.packages("ggplot2")

Load them with library function:

library("cluster")
## generate 25 objects, divided into 2 clusters.
x <- rbind(
  cbind(rnorm(10, 0, 0.5), rnorm(10, 0, 0.5)),
  cbind(rnorm(15, 5, 0.5), rnorm(15, 5, 0.5))
)
clusplot(pam(x, 2))

## add noise, and try again :
x4 <- cbind(x, rnorm(25), rnorm(25))
clusplot(pam(x4, 2))

Functions

square <- function(x) {
  x^2
}
square(3)

## [1] 9

s <- c(1, 2, 3, 4)
square(s)

## [1]  1  4  9 16

square(B)

##      [,1] [,2] [,3]
## [1,]    1    4   16
## [2,]    4    9   25

Loops and if statements

for (i in 1:10) {
  if (i == 1) {
    print(paste("The first number is", i))
  } else {
    print(paste("The next num is", i))
  }
}

## [1] "The first number is 1"
## [1] "The next num is 2"
## [1] "The next num is 3"
## [1] "The next num is 4"
## [1] "The next num is 5"
## [1] "The next num is 6"
## [1] "The next num is 7"
## [1] "The next num is 8"
## [1] "The next num is 9"
## [1] "The next num is 10"

while (i < 10) {
  print(paste("The next num is", i))
  i <- i + 1
}

Reading and writing data

getwd() # get working directory --> setwd("path") = set working directory

## [1] "c:/Users/smoli/Data/Matfyz/05-III-ZS/Multivariate-linear-analysis/labs"

music <- read.csv("datasets/music.csv")
head(music, 10)

##                 X Artist Type     LVar      LAve  LMax   LFEner     LFreq
## 1   Dancing Queen   Abba Rock 17600756 -90.00687 29921 105.9210  59.57379
## 2      Knowing Me   Abba Rock  9543021 -75.76672 27626 102.8362  58.48031
## 3   Take a Chance   Abba Rock  9049482 -98.06292 26372 102.3249 124.59397
## 4       Mamma Mia   Abba Rock  7557437 -90.47106 28898 101.6165  48.76513
## 5     Lay All You   Abba Rock  6282286 -88.95263 27940 100.3008  74.02039
## 6   Super Trouper   Abba Rock  4665867 -69.02084 25531 100.2485  81.40140
## 7  I Have A Dream   Abba Rock  3369670 -71.68288 14699 104.5969 305.18689
## 8      The Winner   Abba Rock  1135862 -67.81905  8928 104.3492 277.66056
## 9           Money   Abba Rock  6146943 -76.28075 22962 102.2407 165.15799
## 10            SOS   Abba Rock  3482882 -74.13000 15517 104.3624 146.73700

dim(music)

## [1] 62  8

write.table(music, file = "datasets/music.txt", sep = ";")