Data Analytics & Visualisation

Question 1

What is the PPDAC process?

Answer 1

A framework for doing data analysis
- Problem
- Plan (What to measure and how)
- Data (collect, manage, process)
- Analysis (reorganise, run analysis, identify patterns)
- Conclusion (Interpret the results)

Question 2

What is structured data?

Answer 2

• Structured Data: Data structured in rows and columns
• Unstructured Data: Data such as Text or audio

Question 3

What are the two general goals and learning paradigms?

Answer 3

• Description of data and knowledge discovery
• Prediction

Question 4

What is supervised learning?

Answer 4

• Inputs and correct output given –> learn the mapping

Question 5

What is unsupervised learning?

Answer 5

• No given output –> model tries to uncover structure on its own

Question 6

What is the objective for interpretative /analytical data?

Answer 6

Understand, summarise, segment & support decisions

Question 7

What are typical sources of interpretative /analytical data?

Answer 7

• CRM data
• Surveys
• Admin data

Question 8

What do the variables for interpretative /analytical data usually look like?

Answer 8

• contracted to be meaningful and stable

Question 9

What are typical results when using interpretative /analytical data?

Answer 9

• Interpretable summaries
• Insights that can be communicated and acted upon

Question 10

What is the objective for Opportunistic / (pure) predictive data?

Answer 10

predict outcomes

Question 11

What are typical sources of Opportunistic / (pure) predictive data?

Answer 11

• Web logs
• App telemetry
• Network traffic

Question 12

What do the variables for Opportunistic / (pure) predictive data usually look like?

Answer 12

• Many; often proxies, individual meaning may be weak or unstable

Question 13

What are typical results when using Opportunistic / (pure) predictive data?

Answer 13

• Models assessed by predictive accuracy

Question 14

What is dimensional reduction?

Answer 14

Combining many starting variables into a final factor

Question 15

What are the two command types in R-Studio?

Answer 15

• Expressions
• Assignments

Question 16

What are expressions?

Answer 16

Something that R can evaluate to produce a value
- E.g. 3+5

Question 17

What are Assignments?

Answer 17

Assignments store the result of an expression in a variable
- E.g. x <- expression

Question 18

How are expressions separated?

Answer 18

• New line or ;

Question 19

How can you group expressions?

Answer 19

• using brackets ()

Question 20

What are the assignment operators? (How is a value assigned?)

Answer 20

Either = or <-

Question 21

How can we allow multiple expressions treated as one unit?

Answer 21

• {}

Question 22

What is a vector?

Answer 22

• Ordered collection of elements of the same type

Question 23

What are the basic vector types?

Answer 23

• Numeric (double) –> floating point possible
• Numeric (integer) –> Whole numbers only
• Character
• Logical

Question 24

How can you compute the variance of a vector ?

Answer 24

• var(x)

Question 25

What are the different types of null values and their meaning?

Answer 25

- Null: Something is actually empty - NA: Something is not available due to missing input - NaN: Something cannot be computed - Inf: An excessively large number or computation

Question 26

What types of operators are there in R?

Answer 26

- Arithmetic (e.g. *, +, /) - Comparison (e.g. >, <=, ==) - Logical (e.g. !, &, |, xor)

Question 27

What is a function?

Answer 27

- A collection of commands to manipulate objects (e.g. make calculations or define new objects)

Question 28

How is a function build?

Answer 28

- A list of arguments between () and separated by ,

Question 29

How can I find out the list of arguments needed for a function?

Answer 29

args()

Question 30

How can we make sure to only print a certain amount of digits after the comma?

Answer 30

, digits = 2

Question 31

What are R objects and what are they classified by?

Answer 31

Anything that can be stored in memory and given a name - Mode (storage type) - Class (How R treats it)

Question 32

What objects are there?

Answer 32

- Vector - Matrix - Factor - Dataframe - Function - List

Question 33

What is a Vector?

Answer 33

A one-dimensional collection of values of the same type - A single column in excel (E.g. C(1,2,3))

Question 34

What is a Matrix?

Answer 34

- A 2D table of values with the same type - Multiples columns and rows

Question 35

What is a Factor?

Answer 35

- A vector of categories

Question 36

What is a dataframe?

Answer 36

A table of columns - Real excel sheet

Question 36

What is a list?

Answer 36

- A container that can hold anything

Question 37

What is a function?

Answer 37

- Object that performs computation

Question 38

How are vectors created?

Answer 38

c(1,2,3)

Question 39

How can you generate a sequence from numerical vectors?

Answer 39

- from integers: 1:2 - From a functions: --> sequence(1,10, by=10) --> rep(1,10) -

Question 39

How can you generate a sequence from character and logical vectors?

Answer 39

- letters[1:5] - paste0("c", 1:10) or paste("c", 10) - rep("female",2)

Question 39

What happens when you put mix types within a vector?

Answer 39

- Vector turns everything to the most flexible type (usually character)

Question 40

How can you generate a random number?

Answer 40

runif(6)

Question 40

How can we asses the length of a vector?

Answer 40

length()

Question 41

How can we assign names to values inside vectors?

Answer 41

names(x)<-c("name1","name2") Combining a character vector with same length of the vector

Question 42

How can we subset a vector?

Answer 42

x[3]

Question 43

How can we remove one or multiple elements from a vector?

Answer 43

x[-3] x[C(-3,-4,-6:-7)]

Question 44

How can we extract elements form a vector using a logical argument?

Answer 44

x[x>10]

Question 45

How can we say that something is not?

Answer 45

!

Question 46

How can we select NA elements in a vector?

Answer 46

x[is.na(x)]