W1: R Functions

Question 1

*

/

+

-

Answer 1

• * : Multiply
• ^ : Power
• / : Divide
• • : Addition
• • : Subtraction

Question 2

How does R display output at the start

Answer 2

With this: (>)

Example

> 6 - 4/2

[1] 4

Question 3

What are logical operators. == != > >= < <=

Answer 3

Provide True or False Response

• == Equality
• != Inequality
• > Greater than
• >= Greater than or equal to
• < Less than
• <= Lesser than or equal to

Example

> 10 < 100

[1] TRUE

> 2 + 2 == 5

[1] FALSE

Question 4

How do we combine logical operators?

&
–
– !

Answer 4

• &: AND
• | :OR
• !: NOT

Example

> c (T & T, T | T, T & !T, T | !T)
[1] TRUE TRUE FALSE TRUE

Question 5

What are functions and arguments

Answer 5

Output = Recipe (Ingredient 1, 2, 3, 4)

• Recipe
  
  • Function
• Ingredients
  
  • Arguments

Example

> sqrt(25)

• Square root
  
  • Function
• 25
  
  • Argument

Question 6

In round (3.14159), which indicate the decimals

Answer 6

• round(3.14159)
  
  • [1] 3
• round (3.14159, 2)
  
  • [1] 3.14
  • 2 indicates decimal place
• round (2, 3.14159)
  
  • [1] 2

If argument names are used explicitly, like round (digits = 2, x = 3.14159, then it doesn’t matter

Question 7

What is sqrt( round(4.65, 2) )

Answer 7

Nested functions goes from inner most to outer most

• sqrt( round(4.65, 2) )
• sqrt (4.65)
• 2.15

Question 8

What are variables and values in R. How are they assigned?

Answer 8

Variables

• Storage to store Values

Values are assigned to variables by <-

Example

Box <- “Gandi”

Variable Box now contains value “Gandi”

Question 9

What are the three types of variables are there?

Answer 9

• Numeric
  
  • Store Numbers
    
    • Box <- 212.23
• Character
  
  • Store Text
    
    • Box <- “Gandi”
• Logical
  
  • Store True/False Values
    
    • Box <- TRUE

Question 10

What are the 5 requirements for Variable Names

Answer 10

• Name must start with letter or a period
  
  • a to z, or A to Z
  • ”.”
• Letters, periods, numbers (0-9) can be used after
• Underscore (i.e, “_”) can also be used, but is best avoided (better to use a period)
• Name cannot contain a space, or characters like ?, +, !, #, $, %, (, ), etc.
• Name cannot be a reserved word, e.g., TRUE or function, that is used in R.

• Names are case-sensitive, therefore, e.g., myColour is different to mycolour, which are both different to
Mycolour, etc.

Question 11

What are Vectors.

What are elements.

What are some requirements

Hence, what are the types of vectors

Answer 11

• Vectors
  
  • Variable with >1 values
• Elements
  
  • Values in the Vector
• Requirement
  
  • Must be the same type, if not R will force them into the same type (Usually character)

Example

• Numeric (Automic) Vector
  
  • > age <- c (34,2)
  • > age
  • [1] 34 2
• Character (Automic) Vector
  
  • > Name <- c(“Dan”, “Alex”)
  • > Name
  • [1] “Dan” “Alex”
• Logical (Automic) Vector
  
  • > Nerd <- c(TRUE, FALSE)
  • > Nerd
  • [1] TRUE FALSE

Question 12

What are advantage of variables

Answer 12

• Store multiple values (vectors), and
• Be combined into data frames.

Question 13

Vectors:
- Identifying

• Dropping
• Selecting

Answer 13

Identify / Select

• Elements can be identified by its position in the vector
  
  • e.g. [1] means show 1^st
• If elements have been named, can be identified by name
  
  • e.g. [“home”]
• Elements can be selected by its position in the vector
  
  • e.g. [c (1,3)] means show 1^st and 3^rd
• Elements can be selected by logical values or logical statements
  
  • e.g. [c (TRUE, TRUE, FALSE)] or if like [boredom <.9] will say [TRUE] to those that are true and [FALSE] to vectors which are false

Drop

• Putting a “-“ sign
  
  • e.g. [-2] means all vectors except the second one

Question 14

In the environmental pane, what do Type, Length, Size, and Values indicate

Answer 14

Type

• Variable type

Length

• No. of elements in the variable

Size

• Amount of computer memory used by the variable.

Values

• (some of) the contents of the variable.

Question 15

What are Data Frames

Answer 15

Collection of variables “bundled” together column-wise.
Organised as a case-by-variables matrix

Row:

• Values for one case or person on all variables.

Column

• Values for one variable over all cases.

Question 16

What are Factor Variables

Answer 16

• Nominal categorical variables
  
  • May look like character variables, but they are not

Question 17

What are continuous variables scaled as

Answer 17

Stored as numeric type variables in R

But they are not truly continous (Computer limits at 15-17 signif)

Question 18

How do we create factors

Answer 18

factor() or as.factor

Question 19

How do we label levels of the factor. Example

Answer 19

levels(eyes) <- c( “brown”, “blue”, “green” )

Question 20

What are R Scripts

Answer 20

Particular text file (with file type “.R”) that contains all the commands required to undertake the analysis.

Question 21

What does expt$age do. How do we select the first case?

Answer 21

expt = From the data file

age = Select the variable

• expt$age[1] or expt{1, “age”]

Question 22

What is the default rounding for signif

Answer 22

Default: 6, but can specify too

• signif( x = 3.1415926535)
  
  • [1] 3.14159
• signif (x = 314159.26535)
  
  • [1] 314159
• signif( x = 3141592653.5)
  
  • [1] 3141590000
• signif( x = 3.1415926535, digits = 3 )
  
  • [1] 3.14

Question 23

How do we create headers, bullets, numbers, italics, bolded, italic bolded, superscript, subscript, strike-through (lol)

Answer 23

• Headers: #
• Bullet: -
• Numbers: 1
• Italics: *
• Bolded: **
• Italics Bolded: ***
• Superscript: ^^
• Superscript: ~ and ~
• Strike-Through: ~~and~~