R fundamentals 1:variables, operators and vectorized operations

文章目錄

• • variables and environment
  • • make custom environment
    • assign new variable in the custom environment
    • get variables from a custom environment
  • operators
  • • arithmetic operator
    • • exact divison
      • integar division
      • modulus
      • exponent
      • format big numbers without a scientific notation
    • mathematical functions
    • • absolute function
      • factorial
      • log function
    • set global settings
  • special numbers
  • • benefits
    • data overflow
    • • "Inf" for positive infinity
      • check if the calculation is infinite
    • undefined
    • • "NaN" for no mathematical sense
      • check if NaN
    • missing value
    • • "NA" for missing value
      • check if missing value
  • logical operator
  • • "|"for or
  • vectorized operations
  • • benefit
    • vector concept
    • vectorized operation FLavor 1:
    • vectorized operation FLavor 2:
    • vectorized operation Flavor 3:

variables and environment

match.score=300

match.score

make custom environment

test=new.env()
           

assign new variable in the custom environment

test$x=300
           

get variables from a custom environment

test$x
           

operators

arithmetic operator

exact divison

10/3
           

integar division

division with an integer outcome

10%/%3
           

modulus

10%%3
           

exponent

10**5
           

format big numbers without a scientific notation

format(10**5,scientific = FALSE)
           

mathematical functions

absolute function

abs(-5)
           

factorial

factorial(3)
           

log function

natural number e as the base

log(2)
           

choose a log base

log(2,base=2)
           

set global settings

lots of default settings in Rstudio

options()
           

change the decimal digits

In default, decimals have 7 digits after the point

options(digits = 10)
           

pi with 10 digits after the point

special numbers

benefits

for data overflow, no mathematical sense, missing data

for program execution or to terminate the adverse program gracefully

data overflow

1/0
           

“Inf” for positive infinity

Inf+1
           

check if the calculation is infinite

is.infinite(1/0)
           

undefined

Inf/Inf
           

“NaN” for no mathematical sense

NaN is short for “not a number”

check if NaN

is.nan(Inf/Inf)
           

missing value

“NA” for missing value

NA+5
           

check if missing value

is.na(NA+5)
           

logical operator

2>3
           

"|"for or

T|F
           

vectorized operations

benefit

explicit coding, no need for loop

vector concept

vector: the one-dimensional set of value of similar type

student.scores=c(1,2,3)
           

vectorized operation FLavor 1:

__ input a vector and output a scalar__

mean(student.scores)
           

vectorized operation FLavor 2:

input a vector and output a vector

final.marks=student.scores+5

final.marks

final.marks>2
           

vectorized operation Flavor 3:

input multiple vectors and output a vector

math.scores=c(1,2,3)
sports.scores=c(2,3,4)
total.scores=math.scores+sports.scores
total.scores