STA100 Lab3

Lab Assignment 1 (Lab projects?)

• Go though LabAssignment1.pdf LabAssignment1.pdf

• Download and open LabAssignment1.Rmd LabAssignment1.Rmd in RStudio and run codes!

• Open template.Rmd and save as a new .Rmd file for your Lab Assignment submission. Edit the author name, date and content.

• Copy the codes in LabAssignment1.Rmd to your new .Rmd file and run the codes.

• Try to modify the codes according to the instruction in LabAssignment1.pdf. Run and see if you can get some numbers. Knit to see how the .pdf looks like.

• Tidy up the codes and writings. Knit and submit!

R and RStudio continue

Follow the below instructions to make yourself comfortable in using R/RStudio for statistical/scientific computing.

Working directory

Working directory is the default folder in which files are saved and read.

• In the Files tab, find/create a folder for your STA100 work. Click More then Set As Working Directory.

• Open the R script you worked on last week. Run the codes.

• Working directory is not persistent after you you close the R/RStudio. Remember to set working directory each time you open a R/RStudio.

Simulations/Sampling

• Let’s draw a sample of random numbers which follows normal distribution with mean 2.5 and standard deviation 1.2

n <- 1000
x <- rnorm(n, mean = 2.5, sd = 1.2)

hist(x)

mean(x)

## [1] 2.508808

sd(x)

## [1] 1.196989

• Let’s draw random samples from BTS

  

bts <- c("Jin", "Suga", "J-Hope", "RM", "Jimin", "V", "Jungkook")

What is the size of bts?

length(bts)

## [1] 7

Sampling!

subgroup_a <- sample(bts, 4, replace = FALSE)
subgroup_b <- sample(bts, 4, replace = FALSE)

subgroup_a

## [1] "Suga"   "Jimin"  "J-Hope" "V"

subgroup_b

## [1] "Jungkook" "Suga"     "Jin"      "J-Hope"

What are the union and intersection of the subgroups?

union(subgroup_a, subgroup_b)

## [1] "Suga"     "Jimin"    "J-Hope"   "V"        "Jungkook" "Jin"

intersect(subgroup_a, subgroup_b)

## [1] "Suga"   "J-Hope"

Set	Elements	Size
BTS (Population)	Jin, Suga, J-Hope, RM, Jimin, V, Jungkook	7
Subgroup A (Sample)	Suga, Jimin, J-Hope, V	4
Subgroup B (Sample)	Jungkook, Suga, Jin, J-Hope	4
A or B (Union)	Suga, Jimin, J-Hope, V, Jungkook, Jin	6
A and B (Intersect)	Suga, J-Hope	2

Help/Documentation

Read the R Documentation of the functions you learn today. Enter the following codes, one by one, and read the corresponding documentation/help in the Help tab.

?rnorm

?mean

?sd

?hist

?length

?sample

?union

?intersect

How Po knows all those built-in functions in R?

• Way 1: Google it

• Way 2: Read R Help/Documentation

Give a man a fish and you feed him for a day; Teach a man to fish and you feed him for a lifetime.

Po	Codes in labs	Google	R Documentation
Fisherman	Fish	Fish Rod	Sea

More R tutorial

• Interactive R course lessons swirl https://swirlstats.com/students.html

  Install swirl with the following commands.

  # If you haven't installed the swirl package yet
  install.packages("swirl")
  library(swirl)
  install_course_github("swirldev", "R_Programming_E")

  After swirl is installed (you only need to do it once), you can start/resume the R tutorial with the commands:

  library(swirl)
  swirl()

  Schedule some time to go though all the lessons by yourself! Almost all of the R codes you need to know are here in those lessons.

• If you prefer more static readings (Po did read them to learn R!):

  • R for Beginners https://cran.r-project.org/doc/contrib/Paradis-rdebuts_en.pdf
  • An Introduction to R https://cran.r-project.org/doc/manuals/r-release/R-intro.pdf

• If you like RStudio’s data science things,

  • R for Data Science https://r4ds.had.co.nz/
  • RStudio Primer https://rstudio.cloud/learn/primers/