Statistics and Statistical Programming (Winter 2017)/R lecture outline: Week 3

Review of material from class

• loading data:
  • load() versus read.csv()
  • when things don't coopreate...
  • library(foreign)
• defining functions
  • syntax for defining functions: show the my.mean function
  • calling functions (your own or others) with apply(), lapply(), sapply()
• stuff related to distributions
  • rep()
  • seq()
  • sample(); and sampling into data.frames

Online only

• dates with POSIXct(). dates will almost always be given to you as characters, and you need to parse them
• tapply(), and putting things back into data.frames
• merge()

Skipped for now

• ordered() — really just a type of factor for ordinal data

• • distribution functions: lets focus on *unif(): the key is on page 222 of Verzani
    • The “d” functions return the p.d.f. of the distribution
      • dunif(x=1, min=0, max=3) # 1/3 of the area is the to the left 1
    • The “p” functions return the c.d.f. of the distribution.
      • dunif(q=2, min=0, max=3) #1/(b-a) is 2/3
    • The “q” functions return the quantiles.
      • qunif(p=0.5, min=0, max=3) # half way between 0 and 3
    • The “r” functions return random samples from a distribution.
      • runif(n=1, min=0, max=3) # a random value in [0,3]
• running quick simulations
  • lets look at the relationship between mean and standard deviation on a 1 through 10 likert scale