Packages

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# Packages

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## Are you struggling?

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# Plan for today

- Brief recap
- **Packages**

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# Recap of using variables
- Most of the time, we want to do more than add, subtract, multiply etc.

- We want to act on our variables. We do this with operators & **functions**
  - *Each function* has a unique name
  - *Each function* requires some input, and the function can be modified using arguments
  - *Each function* will produce an output

- Remember:
  - objects are *nouns*
  - functions & operators are *verbs*
  - arguments are *adverbs*
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# Recap of using variables
Where do you find functions?
  - Some exist in `R` by default
    - `t.test()`
    - `cor()`
    - `scale()`

Lots of people all over the world write their own functions. And they (rightly!) think it's useful to share these functions.
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# Packages
What is a **package**?
 - A collection of functions and datasets
 - Open source
 
Packages are the reason R is so powerful!
 - While you can definitely write your own functions, most of what you need to do someone else has already done for you! 
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# How do I get packages?
Packages can be downloaded from the *CRAN* (*C*omprehensive *R* *A*rchive *N*etwork)

You will do this from inside `R`

.center.medium.box-inv-6[Need to be connected to the internet!]
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# 2 ways to install packages

1. Install button in the Packages tab

2. R Code
 
 
 
 
.center.large[*Either way, you need to know the name of the package*]
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# Install Button
<img src="06-slides_files/figure-html/p10.png", width = "85%">
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# Install Button
<img src="06-slides_files/figure-html/p11.png", width = "85%">
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# Install Button
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# R code to install packages
 
 
 
 
 
 
 
.center.middle.medium[`install.packages("psych")`]
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# Packages

INSTALLING
  - Downloading the package and saving it to your computer
  - Like installing Microsoft Word on your computer
  - Do this **ONCE**
  
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LOADING
  - Like opening Microsoft Word to write a paper
  - Once a package is loaded, you can use all of it's functions and datasets are ready to use
  - You need to do this **EVERY TIME** you open a new `R` session
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# 2 ways to load packages
1. Checkbox in the packages tab (not recommended)

2. R code
 
 
 
 
.center.large[*Either way, you need to know the name of the package*]
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# R code to load packages
 
 
 
 
 
 
 
.center.middle.medium[`library(psych)`]
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# Dependencies
<img src="06-slides_files/figure-html/p13.png", width = "65%">

Uses functions from other packages

Installed automatically

Loaded automatically
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# Help! (again)

Ways to find documentation:

.medium[`?psych`] -- opens documentation specific to that pacakge or function

.medium[`??psych`] -- searches for this in all documentation (that you have installed and loaded)

To find a package that does what you need: .large[Google]

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# Summary

.box-inv-6.small.left[**Packages** are a collection of functions and data sets]
  1. You **install** the package once; must be connected to the internet
  2. You **load** the package every time you use it; do not need to be connected to the internet
  
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.box-inv-6.small.left[How do you find the function you need? How do you now what package it's in?] 
- **G-o-o-g-l-e!**
- "structural equation modeling in R"

.box-inv-6.small.left[How do you know how to use the function? What are the function's **arguments**?]
- Help documentation in R
- `? function.name`