## 1.1 How to use R

# Q1.1.2
# Order of calculations is as you would expect and brackets work as you are used to

## Variables
# Q1.1.4 The program outputs 1, which is the value of x

# Q1.1.5 
x+5
x*5
x*5+x
# all of these work you would assume

# Q1.1.6 
y <- 5*20
# y only saves the output of the calculation, not how we got there

# Q1.1.7 
z <- x+y

# Q1.1.8 
# does not save changed value:
z+10
#saves changed value:
z <- z+10

## Functions

a <- sum(1,2,3)

# Q1.1.10 function is 'sum', argument is 1,2,3, and output (6) is saved in variable a

# Q1.1.11 The output is exactly as one would expect

# Q1.1.12 
# getwd() finds your current working directory (wd) 

## 1.2. Simple data types

## Numbers ("numeric")
# Q1.2.1 
typeof(x) # double
typeof(5.1) # double
typeof(pi) # double
typeof(2L) # integer, the large L indicates that R should interpret this as integer and not double

## Characters (text)
# Q 1.2.2 
typeof('abc') # character

# Q1.2.3 
# we cannot do addition on numeric value and character, they are not compatible

## Logical (Boolean, i.e. TRUE or FALSE)
# 
# Q1.2.4 
x < 10
y == 20

## Vectors
# 
# Q1.2.5 
# output is 
#  1  2  3  4  5  6  7  8  9 10
# and it is type integer (which is the type of the elements in the vector)

#   Q1.2.6 
# vector1 and vector2 are not the same. 
# the argument by tells seq how large jumps it should make between numbers
# the argument length tells seq how long the resulting vector should be

# Q1.2.7 
vector3 <- seq(40,100,by=10)

# Q1.2.8 
charactervector <- c('a','b','c')

## Vector indexing

# Q1.2.9 
vector3[2]
# returns 50

# Q1.2.10 
# you can use :
vector1[1:2]
# or you can use c()
vector1[c(1,2)]

# Q1.2.11 
# running this returns the values from vector1 which are TRUE in the logical vector

# Q1.2.12 
# this returns a logical vector stating for which of the elements the logical operation is true and false
# if we wanted to get the relevant values, we could run
vector1[vector1>10]

# Q1.2.13 
vector3[vector3>50 & vector3<80]

## 1.3 Loops
# Q1.3.2

# we only need to change the years on the first line (the header)
for(i in 2020:2025){
  print(paste0("Is this year ",i,"?"))
}

# Q1.3.3
# before the loop we initialise a variable with 0
currvalue <- 0

for(j in 1:100){
  # the next line takes whatever currvalue has at that iteration and adds j, and saves these as currvalue for next iteration
  currvalue <- currvalue + j 
}
# print out the final value
currvalue
# double check that our result is correct
sum(1:100)
# it is! yay!

# 1.4 Packages
# Q1.4.1
install.packages('psych')
# Q1.4.2
library(psych)
# Q1.4.3
describe(vector1)
 

Created by Juulia Suvilehto
juulia.suvilehto@iki.fi

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