Advanced quantitative data analysis

class: center, middle, inverse, title-slide

.title[
# Advanced quantitative data analysis
]
.subtitle[
## Introduction
]
.author[
### Mengni Chen
]
.institute[
### Department of Sociology, University of Copenhagen
]
.date[
### 04/09/2024
]

---

#Introduction
About me 
- Assistant professor in Copenhagen University (05/2021-now)
  - Teaching: population and society, family sociology, advanced quantitative data analysis
  - Research: family formation and dissolution, fertility, ageing, population health, population policies
  
- Research Experience: Cologne University, Germany; Catholic University of Louvain, Belgium; Wittgenstein Centre, Austria

- Phd in University of Hong Kong (2013-2017)

- My office hour: Every Tuesday 10:30-11:30 am, Room 16.1.48, Building 16

---
#Introduction
About you
- Name

- Year and department

---
#Introduction
About what you know

[I would like to know what you have known about R and statistics](https://docs.google.com/forms/d/e/1FAIpQLSdrKGGUIC_RO21DPaBciM0DIiKGMlJPL36iaMZCXCXyp9e6tw/viewformLinks to an external site. )

---
#About the course
- Main content
  - Intro to R
  - Cross-sectional data analysis: OLS, OB-decomposition
  - Panel data management
  - Panel data analysis I: fixed effect
  - Panel data analysis II: difference in difference
  
- Learning approach
  - Lecture 
  - Small in-class exercise
  - Bring lap-top every class
  - Fagcafe after class, Wednesday 15:00-17:00, Room CSS 2-1-12.
    -   Julie Olea Brønnum Cordes and Yanzhen Luo are our TAs.
  
---
#Assessment
  - Portfolio of 3 assignments: select one of the three topics
    - P1: 3 pages for introduction, theories, and OLS regression
      - Deadline is Oct.27, 23:59.
    - P2: 3 pages for describing what is fixed effect and applying fixed effect
      - Deadline is Dec.01, 23:59.
    - P3: 3 pages for  describing what is DID and applying DID
      - Deadline is Dec.15, 23:59.
    - Please submit your portfolio even if it is not 100% complete.
  - A final combined product for exam: max 10 pages for all 
    
  - Individual or group work: 10 + 5 pages per extra person
  - Final exam: 13 January 2025, uploaded in Digital Exam before 12:00 (noon, Danish Time) 
  - Re-exam: 10 February 2025, written exam with new questions

---
#Feedback
  - Portfolio 1: all get feedback from the teacher
  
  - Portfolio 2: randomly 50% get feedback from the teacher + peer feedback
  
  - Portfolio 3: the rest 50% get feedback from the teacher + peer feedback
  
  - Overall, everyone gets twice feedback from the teacher + twice peer feedback

---
#Three topics to choose
- Q1: How does first childbearing affect women’s subjective wellbeing of women?

- Q2: How does entry into a partnership affect people’s subjective wellbeing?

- Q3: How does partnership break-up affect people’s subjective wellbeing?

- **Choose one topic for all your 3 portfolios**
- The aim of 3 portfolios is to answer the chosen question using 3 different methods.
---
#How to measure subjective wellbing
You can choose one of the following measurements as your outcome variable:

- Subjective satisfaction with work

- Subjective satisfaction with leisure activities

- Subjective satisfaction with family

- General life satisfaction
---
#Access to the Pairfam data
- [What is pairfam](https://www.pairfam.de/en/)

- [What you need to know about pairfam: see Tutorial 8-12](https://www.pairfam.de/en/documentation/video-tutorials/)

- How to access to pairfam
  - Fill up the form: go to absalon → this course → files → Data → **TeachingVersion_pairfam13.0_Cov-19_en.pdf** → send to support@pairfam.de

---
#How to use ChatGPT in the course
  - How many of you using ChatGPT
  
  - What you use it for
  
  - Is it ok to use?
    - yes: check codes, ask questions, get some ideas 
    - no: just copy the codes without understanding what you are copying
    - mindful and critical

---
#Other info
- Datacamp is a platform you can have afterclass exercise and instruction.

- Absalon setup
  - Data: go to absalon → this course → files → Data
      - Women data: can used to answer Q1
      - 50%data: can be used to answer the Q2 and Q3
      - Codebook Anchor_en, pairfam Wave 1 2008-09
      - Variables, pairfam Waves 1-13.xlsx
    
  - Reading: go to absalon → this course → files → Reading
      - Example reading
      - Week40-41, Week-43-45, Week46-47, Week48-49
  
  - Assignment examples: portfolio examples from previous cohorts

---
#What is R
If you're mainly interested in using regression to analyze a specific survey, it is
1. ...a rather tedious stats programming language.

2. ...basically a calculator:

```r
1+1
```

```
## [1] 2
```

```r
x <- 1
x+1
```

```
## [1] 2
```

---
#What is R
If you enjoy coding and working with several data sources at once, it is

1. ... a great platform for (social) data science of

2. ... networks, text, geo, pictures...

3. ... an all in one solution.→  I coded these slides in R!

4. ... a huge, dynamic and cooperative community.

5. ... a very higher chance to get a job in Danish labor market!

[why you should use R](https://www.youtube.com/watch?v=9kYUGMg_14s&list=PLbh5g6tUnVSRwojrTf-ZBTXeCs-oYh9DV&index=94&t=3s)

---
#What is R

![](https://pbs.twimg.com/media/CiSMsEpXEAATXry?format=jpg&name=small)

---
#What you will learn in R

(Social) Data Science

![](https://d33wubrfki0l68.cloudfront.net/571b056757d68e6df81a3e3853f54d3c76ad6efc/32d37/diagrams/data-science.png)

.backgrnote[*Source*: Grolemund and Wickham (2017)]

<src="https://d33wubrfki0l68.cloudfront.net/571b056757d68e6df81a3e3853f54d3c76ad6efc/32d37/diagrams/data-science.png" width="70%" style="display: block; margin: auto;" >

---
#Install R and R
- [First, download R and install](https://www.rstudio.com/products/rstudio/download/#download)
- [Second, download R studio and install ](https://www.rstudio.com/products/rstudio/download/#download) 
- Video on how to install them in [Windows](https://www.youtube.com/watch?v=_2sewGCA0y4) and [Mac](https://www.youtube.com/watch?v=LanBozXJjOk)
- If you don't manage to install R and Rstudio, you can use [Rstudio cloud](https://posit.cloud/)
- [Video on how to use Rstudio cloud](https://www.youtube.com/watch?v=uK1Va_UWQFc)

---
#Interface in R
<img src="https://d33wubrfki0l68.cloudfront.net/8a64bb047429d7ae0e2acae35c40e421e6439bf6/80e5d/diagrams/rstudio-editor.png", width="550px" height="550px"
 style="position:absolute; top:120px;">

---
# R Studio workflow
1. Use **Projects** to manage all files (scripts, data, figures and tables) belonging to the same project.
2. Use **R scripts** to write down your codes, so you can reproduce your results by running the codes in the R script.

<img src="https://d33wubrfki0l68.cloudfront.net/8a64bb047429d7ae0e2acae35c40e421e6439bf6/80e5d/diagrams/rstudio-editor.png", width="450px" height="450px" 
 style="position:absolute; right:200px; top:220px;"> 
---
#Set up your own Rproject and Rscript
- Click on the Project button.
 - "New Directory"
 - "New Project"
 - Finally, a name for the folder and under "Browse" where you want that folder to be located.
 - Done! Now you should find an empty folder under the path your wanted it to be set up.
 - In the future, start RStudio by double clicking on the project icon in your folder.
- You can follow the procedures to create your R project and R script in [this website, click here](https://rpubs.com/fancycmn/1213843).

- [Video on creating a project: 3'38-7'32](https://www.youtube.com/watch?v=wqOme7xsZvs)
- [Video on openning an existing project: 9'35-10'29](https://www.youtube.com/watch?v=wqOme7xsZvs)

---
#R scripts (wait and see)
OK, you are good to go!

Pro tip: Use the R Script to take notes during the lecture!

**# take notes**

```r
#take notes
x <- 1
x+1
```

```
## [1] 2
```
---
#First steps with R
- Creating objects
 - R is an object-oriented programming language. We create objects with the assignment operator
 
- The assignment operator may be used in both directions: <-, or ->. This can help you write more legible code.
 - Shorthand in Windows, press **alt** and **-** together
 - Shorthand in Mac, press **Option** and **-** together
 
- Run code
 - For Windows, press **Ctrl** and **enter** together
 - For Mac, press **cmd** and **enter** together

---
#First steps with R
- Creating objects
  - Objects can contain all kinds of information.

```r
# Create a new object "test_object" and assign to it the result of 5 + 2
test_object <- 5 + 2
#printing the result: type test_object in the "Console" and see what you get
test_object
```

```
## [1] 7
```

```r
# text can also be an object
text_object <- "I love this course so much!"
#pring the results: type text_object in the "Console" and see what you get
text_object
```

```
## [1] "I love this course so much!"
```

---
#First steps with R
compare the two sets of codes

```r
test_object1 <- 5+2
test_object1 + 3
test_object1
```

```r
test_object2 <- 5+2
test_object2 <- test_object2 + 3 
test_object2 
```
--
If you don't use the assignment operator (<-), R will simply print the result of an operation without changing that object (i.e., without any further consequences).

If you actually want to create or modify objects, you need to use the assignment operator and explicitly assign the result of your operation to the object you want to change.

---
#First steps with R
Use functions:

function_name(argument1 = value1, argument2 = value2, ...)

Example 1: The **seq()** function, for instance, produces a sequence of numbers and has (among others) the arguments from and to.

```r
(yet_another_object <- seq(from = 1, to = 5))
```

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

```r
#or a shorter code
(yet_another_object <- seq(1, 5))
```

```
## [1] 1 2 3 4 5
```
---
#First steps with R
Example 2: The class() function tells you what class/type of object your are dealing with:
--

```r
class(yet_another_object) # "yet_another_object" contails whole numbers, so it is:
```

```
## [1] "integer"
```
--

```r
class(text_object) # "text_object" contains a sentence, so it is:
```

```
## [1] "character"
```
--

```r
class(seq)
```

```
## [1] "function"
```

```r
#Try to run
alphabet <- seq(from = "a", to = "z")
```
--
Functions will throw an error message, if you feed them with an object of a class it cannot handle.
---
#First steps with R
Arithmetic operators: plus=+, multiply=*, power=^, square root=sqrt()
--

```r
2 + 3 
```

```
## [1] 5
```

```r
2 * 3 
```

```
## [1] 6
```

```r
2^3   
```

```
## [1] 8
```
--

```r
sqrt(yet_another_object) #square root as a function
```

```
## [1] 1.000000 1.414214 1.732051 2.000000 2.236068
```

---
#First steps with R
Logical operator

- and = **&**;
- or = **|**;
- not= **!**;
- belong = **%in%**;
- equal = **==**;
- not equal= **!=**;

---
#Logical operator in action

```r
x <- 2
x==3
```

```
## [1] FALSE
```
--

```r
x!=3
```

```
## [1] TRUE
```
--

```r
x > 5 & 6 # greater than 5 and greater than 6
```

```
## [1] FALSE
```
--

```r
x > 5|1 # greater than 5 or greater than 1
```

```
## [1] TRUE
```
--

```r
x > (5 & 6) | (1 & 2) # more complex comparison
```

```
## [1] TRUE
```
---
#Getting help in R
R has a steep learning curve and is, at times, simply frustrating. The documentation of a specific function can be accessed via typing **?<Name of function>**

```r
?seq
?sqrt
```

---
#Take home
1. R is an object-oriented programming language. Objects are basically containers and they can contain anything: data, functions, other objects, results, figures, and more ... Objects can be called by their name, which needs to start with a letter. If you just type the name of an object, R prints the object.

2. Functions do stuff with objects, which we assign as values to a function's arguments. What exactly a function does, depends on the class of an object. Functions themselves are objects too.

3. Important code
- "?": View a function's help file.
- "#": defines a comment in your code. Comment as much as possible!
- "<-": is the assignment operator of R.
- +, -, *, ^ : Arithmetic operators
- & means "and", | means "or", ! means "not", == means testing whether the two are equal 
- class(): tells you the class of an object

**Reference**: Grolemund, G. and H. Wickham (2017). R for Data Science. O'Reilly.

---
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---
class: center, middle
#[Exercise: 1-6 necessary; 7-9 optional](https://rpubs.com/fancycmn/1214111)