BIO259 Lecture 01

• How to use R

• a <- 5 #storing values in vars
  a
  

• # typecasting
  a <- 12321.34124
  as.integer(a)
  a
  12321
  

• a <- 1
  b <- 2
  a + b
  sum(a,b)
  sum(a,b, na.rm=T) #remove not applicable values so there's no runtime error.
  a - b
  a * b
  prod(a,b)
  a/b
  a^b
  typeof(a+b) # same as instanceOf(a) in java
  

• # Strings
  word1 <- "hello"
  word2 <- "world"
  word1
  'hello'
  'world'
  paste() # binary operator on strings to add and output one string
  c() # put things in a box together, like an array of type strings
  word3 <- paste(word1, word2)
  word3
  'hello world'
  word4 <- c(word1, word2)
  word4
  'hello' . 'world'
  # change the seperator
  word6 <- paste(word1, word2, sep="")
  word6
  'helloworld'
  

• See that there's a difference between paste and c

• length(word3)
  1
  length(word4)
  2
  

• names <- c("Alice", "Bob")
  ages <- c(30, 25)
  names
  'Alice' . 'Bob'
  30 . 25
  
  paste(names, "is", ages, "years old")
  'Alice is 30 years old' . 'Bob is 25 years old'
  

• True and False

• flag1 <- T
  flag2 <- TRUE
  flag3 <- F
  flag1 & flag2
  TRUE
  flag1 & flag3
  FALSE
  flag1 | flag3
  TRUE
  !flag1
  FALSE
  typeof(flag1)
  'logical'
  

• a <- 5
  b <- 3
  x <- a > b
  x
  TRUE
  y <- a < b
  y
  FALSE
  # you have == as well as !=. Also = where = means <- like python assignments and java.
  typeof(a)
  'double'
  typeof(x)
  'logical'
  typeof(a > b)
  'logical'
  

• Vectors

• n <- c(1,2,3,4,5)
  l <- c("a","b","c","d","e")
  length(n) == length(l)
  TRUE
  t <- c(T,F,T)
  # Access List / Array
  n[2]
  2 # NOT ZERO INDEXED
  l[5]
  'e'
  l[6]
  NA
  

• Create a subset:

• n[n > 3]
  4 . 5
  n[n != 3]
  1 . 2 . 4 . 5
  

• Data hierarchy:
  • $\text{Logical}\to \text{Numeric}\to \text{Character}$
  • Lowest category wins

  • a = c(3.14, "pi")
    a
    '3.14' . 'pi'
    typeof(a)
    'character'
    b = d(T, 42)
    b
    1 . 42
    typeof(b)
    'numeric'
    

  • You also have as.numeric() to your disposal too.

  • a <- T + T
    b <- T + F
    a
    2
    b
    1
    

  • If you don't want R to auto convert your data in the array, create a list.

  • mixed <- c(T, 42, "test")
    mixed
    'TRUE' . '42' , 'test'
    chr [1:3] "TRUE" "42" "test"
    mixed <- list(T, 42, "test")
    mixed
    TRUE . 42 , 'test'
    str(mixed)
    List of 3
     $ : logi TRUE
     $ : num 42
     $ : chr "test"