Write Readable Code

layout: true
  
<div class="my-footer"><span>ouzhang.me/talk/readable_code</span></div>

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name: xaringan-title
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# Write Readable Code

### .fancy[Simple and Practical Techniques for Better Statistical Programming]

.large[Ou Zhang | Summer Intern::Seminar 2018]

---
class: right, middle

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---

# .center[Agenda]

What is the readable code?

Why we need to write readable code?

Factors Influence Code Readability

Version Control

Q & A

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name: why
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# .fancy[Why I give this talk to **Psychometrician** and **statistical analyst**?]

---

# .center[Key elements to success]

- Content Knowledge

- Psychometrics skills

- Programming

--
  
## .center[Good programming means <p style="color:red"> Work efficiency</p>]

---
# .center[Disclaimer]

I am presenting what I consider the <span style="color: red;">best<span/> practice.

I acknowledge that there are other ways of doing things.

Suggestions & Personal Opinion <span style="color: blue;">(Biased)<span/>

You may have your own opinions or existing standards and...

## .center[<span style="color: red;">**it is completely fine.**<span/>]

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name: ugly code runs

# .center[Ugly code runs]

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name: what is good code
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# .fancy[What is readable code?]

---
# .center[A readable code is...]

Easy to read & understand

Easy to extend & reuse

Gives reliable results

Easy to maintain

Testable

Easy to share with others

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name: why write a readable code
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# .fancy[Why write a readable code?]

---
## .center[Why write a readable code?]

People often share their code with others

Code might be adapted or modified by others

![](img/reuse_code.jpg)

---
## .center[More importantly, the code is...]

For your <span style="color: red;">**FUTURE SELF**<span/>

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name: two concept
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# .fancy[Readable code vs. Efficient code]

---
## .center[Readable code vs. Efficient code]

Code efficiency is directly linked with algorithmic efficiency and the speed of runtime execution for software. It is the key element in ensuring ** computer** high performance

Code readability is directly related to the most important qualities of code. If code is easy to read **by the user**, it will be easy to understand which makes it easier to debug, maintain and extend.

---
name: Focus
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# .fancy[Today's focus: Code Readability]

---
## .center[Code Readability]

>"Programs must be written for people to read, and
only incidentally for machines to execute."

.right[Abelson & Sussman, Structure and Interpretation of Computer Programs]

> At present, the work efficiency bottleneck is **human brain** not machine.

.right[Hadley Wickham]

---
name: what do you mean
class: center, inverse, middle

# .fancy[What do you mean by readable code?]

---
## .center[What do you mean?]

Keep it simple, Keep it short.

At least, keep the **module** simple and short.

---
## .center[Key elements of readable code]

.pull-left[

Readable – clarity in the structure and content of the code

* is easy for the user to read
* is as self-explaining as possible

]

.pull-right[

]

---

## .center[Key elements of readable code]

.pull-left[

Shareable – how quickly and easily someone new can understand and modify your code

]

.pull-right[

]

---
## .center[Suggestion]

Don’t implement code that you won’t need

Simplify requirements

Keep your codebase small

Be familiar with libraries around

---
## .center[Good code standards]

Beautiful is better than ugly

Explicit is better than implicit

Simple is better than complex

Complex is better than complicated

Readability counts

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# .fancy[Factors influence code readability]

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## .center[Factors]

Naming convention

Style/ Aesthetic

Commenting

Functions/Macros

* Split Your Code into Short, Focused Units
* Don’t repeat yourself
* Avoid nesting definition

Check errors and Respond to Them

--
Avoid dead code

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name: naming convention title
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background-image: url(img/naming-conventions.png)
background-size: cover

# Naming Convention

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name: naming convention1

# Naming Convention

Adopt a convention and stick with it (fetch vs. retrieve vs. get)

Use intention-revealing names

Avoid misleading readers

Make meaningful distinctions

Use searchable names

Avoid mental mapping

Use domain names

---
name: naming convention2

# Naming Convention ⏭

Avoid Generic Names

Bad name example: <span style="color: red;">v1, v2, v3, temp1</span>

One exception: **well-written, verified function/macro**

Prefer Concrete Names

Example: <span style="color: red;">percent_a, average_item_time</span>, etc.
  
---
name: naming convention3

# Naming Convention ⏭

Use searchable names <span style="color: blue;">(for debugging) </span>

---
name: naming convention4

# Naming Convention ⏭

.pull-left[

Length vs Meaning

Shorter names for shorter scopes

Longer names for larger scopes

]

.pull-right[

<img src="img/Name_is_the_key.PNG" width="100%" style="display: block; margin: auto;" />
]

---
name: naming convention5

# Naming Convention ⏭

.pull-left[

Formatting

* All lower letter
* All UPPER letter
* period.separated
* underscore_spearated
* lowerCamelCase
* UpperCamelCase
]

.pull-right[

Example

* <span style="color: blue;">searchpaths</span>
* <span style="color: blue;">IRT_A</span>
* <span style="color: blue;">item.info</span>
* <span style="color: blue;">expect_theta</span>
* <span style="color: blue;">seq_Along</span>
* <span style="color: blue;">NextMethod</span>

]

<div class="figure" style="text-align: center">
<img src="img/matching_naming_convention.png" alt="From “The State of Naming Conventions in R " width="65%" />
<p class="caption">From “The State of Naming Conventions in R </p>
</div>
---
name: naming convention6

# Naming Convention ⏭

<span style="color: red;">Noun</span> for variable name, object name, class name, property name, arguments name

<span style="color: red;">Verb</span> for function name, method name

Avoid using the same word for two purposes

Ask yourself...

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name: naming convention7 
class: center, inverse, middle

# .fancy[What other meanings could someone interpret from this name?]

---
name: naming convention8

# Naming Convention ⏭

Names That Can’t Be Misconstrued

.right[The State of Naming Conventions in R    – Rasmus Baath]

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name: style_aesthetic title 
class: center, inverse, middle
background-image: url(img/Style-vs-Aesthetics.jpg)
background-size: cover

# .fancy[style & aesthetic]

---
name: style_aesthetic1

# Style and Aesthetics

Use consistent layout

* Indent your code & Vertical and horizontal spacing

* Limit the width of your code per row (80 columns)

* Limit the length of function

Make similar code look similar

Group related lines of code into blocks

---
name: style_aesthetic2

# Style and Aesthetics ⏭

.pull-left[

Coding text

* All lower case text
* All UPPER case text
* CamelCase text

]

.pull-right[

Follow the Style Guide
* [Google’s R Style Guide](https://google.github.io/styleguide/Rguide.html)             
* Code like it matters (Paul Kaefer)
* Hadley Wickham: [Style Guide](http://adv-r.had.co.nz/Style.html)                    
* SAS Programming Guidelines
* [R Style. An Rchaeological Commentary](https://cran.r-project.org/web/packages/rockchalk/vignettes/Rstyle.pdf)

]

---
name: Style suggestion 
class: center, inverse, middle

# .fancy[Write code like you work on your daily writing]

---
name: style_aesthetic3

# Style and Aesthetics  ⏭

.pull-left[

Good example

]

.pull-right[

Bad example

]

---
name: commenting title 
class: left, middle
background-image: url(img/comment.png)
background-size: cover

# .fancy[Commenting]

---
name: comment1

# Commenting

.pull-left[

The purpose of commenting is to help the reader know as much as the writer did.

]

.pull-right[

]

---
name: comment2

# Commenting ⏭

.pull-left[

Recording Your Thoughts

* Include “Director Commentary”
  
* Comment the Flaws in Your Code  
  
* Comment on Your Constants

]

.pull-right[

Put yourself in the reader’s shoes

* Anticipating Likely Questions

* Advertising Likely Pitfalls  
  
* “Big Picture”  
  
* Summary

]

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name: No_comment title 
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background-image: url(img/no_comment.jpg)
background-size: cover

# .fancy[Don’t comment on the facts that can be derived quickly from the code itself.]
---
name: comment3

# Commenting ⏭

Comment while writing your code

<img src="img/Add_comment_is_important.jpg" width="70%" style="display: block; margin: auto;" />
---
name: comment4

# Commenting ⏭

--
.pull-left[

Keep Comments Compact

Describe Function Behavior Precisely

Use Examples

State the Intent

]

.pull-right[

<img src="img/Meaningful_comments.PNG" width="80%" style="display: block; margin: auto;" />
]
---
name: comment5

# Keep comments compact

<img src="img/compact_comment.png" width="80%" style="display: block; margin: auto;" />
---
name: comment6

# Describe Function Precisely

<img src="img/precise_comment.png" width="80%" style="display: block; margin: auto;" />
---
name: comment7

# Use Examples

<img src="img/use_example_comment.png" width="80%" style="display: block; margin: auto;" />
---
name: comment8

# Precise & Compact Comments

<img src="img/Concise_comment.jpg" width="75%" style="display: block; margin: auto;" />
---
name: Good_header
class: center, inverse, middle

# .fancy[Having a good header delivers most information of the code.]
---
name: sas_header

# Header Example 1

<img src="img/sas_header.png" width="75%" style="display: block; margin: auto;" />
---
name: r_header

# Header Example 2

<img src="img/r_header.png" width="75%" style="display: block; margin: auto;" />
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name: loops_logic 
class: center, middle
background-image: url(img/loops.jpg)
background-size: cover

# .fancy[Loops & Logic]
---
name: loop1

# Loop & Logic

--
.pull-left[

Make your logic as “**natural**” as possible

The code is not just “**Get the job done**”.

A good readable code means better work efficiency and better work transition in the future.

]

.pull-right[
<img src="img/how to write good code.png" width="80%" style="display: block; margin: auto;" />
]

---
name: loop2

# Loop & Logic ⏭

Avoid **do/while** Loops

Returning Early form a Function

Minimize Nesting

Flow of Execution
---
name: loop3

# Loop & Logic ⏭

Minimize the time needed for someone to understand it instead of minimizing the number of lines

<img src="img/bad_function.png" width="65%" style="display: block; margin: auto;" />
---
name: loop4

# Loop & Logic ⏭

Breaking Down Giant Expressions

<img src="img/one_bite.png" width="65%" style="display: block; margin: auto;" />
---
name: loop5

# Loop & Logic ⏭

.pull-left[

Explaining Variables

* Summary Variables
  
* Use De Morgan’s Laws
  
* Break Down Giant Statements

]

.pull-right[

<img src="img/Demorgan_laws.png" width="75%" style="display: block; margin: auto;" />
]
---
name: loop6

# Loop & Logic ⏭

Separate data input/output steps from core function modules

.pull-left[

Bad Example:

One Big function:

1. Data input
2. Core calculation
3. Data output

]

.pull-right[

Good Example:

* Function 1: Data input function

* Function 2: Short Core calculation function

* Function 3: Data output function

]
---
name: No_comment title 
class: center, middle
background-image: url(img/modules.png)
background-size: cover

# .fancy[Function, Module, Macro]
---
name: function1

# Function, Module, Macro

One Task <span style="color: red;">Well<span/> at a Time, One Task <span style="color: red;">Only<span/> at a Time

<img src="img/multi_tasking.png" width="65%" style="display: block; margin: auto;" />
---
name: function2

# Function, Module, Macro ⏭

Don't <span style="color: red;">repeat<span/> yourself

<img src="img/repeat_line.png" width="75%" style="display: block; margin: auto;" />
---
name: function3

# Function, Module, Macro ⏭

Bad Example:

<img src="img/bad_repeat.png" width="85%" style="display: block; margin: auto;" />
---
name: function4

# Function, Module, Macro ⏭

Good Example:

<img src="img/good_no_repeat.png" width="85%" style="display: block; margin: auto;" />
---
name: function5

# Function, Module, Macro ⏭

Avoid definition nesting

<img src="img/nesting_function.png" width="85%" style="display: block; margin: auto;" />
---
name: function6

# Modularity

Write code so it is multi-purpose and can be repurposed e.g., macro variables for filenames and date values

<img src="img/macro_driver.png" width="85%" style="display: block; margin: auto;" />
---
name: No_comment title 
class: center, middle
background-image: url(img/version_control.png)
background-size: cover

# .fancy[Version Control]
---
name: vc1

# Version Control

All codes should use version control

Even useful in other fields (writing/editing, anybody who makes presentations or has a resume)

--
Rudimentary strategy is a terrible idea (i.e., code.sas, code_v2.sas, code_new.sas, code_old.sas...)

Use software like git <img src="img/git.png" width="5%"/>&nbsp;, Subversion (svn), Mercurial, etc.

[Youtube tutorial](https://www.youtube.com/watch?v=HVsySz-h9r4)

You will hit some learning curve, but the basics can be taught within 1 hour

Makes sharing easier

Saves you over and over (story time…)
---
name: vc2

# github <img src="img/github.png" width="5%"/>&nbsp;

<img src="img/oz_github.jpg" width="85%" style="display: block; margin: auto;" />
--

You can learn how to use github from this youtube link below

[Youtube tutorial](https://www.youtube.com/watch?v=xuB1Id2Wxak)

---
name: Further Reading

# Further Reading

.pull-left[

]

.pull-right[

]
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# Further Reading

.pull-left[

]

.pull-right[

]
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class: center, middle

# Thanks!