Learn R (Notes)

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Variables

> a <- array(1:20, dim=c(4,5))

> typeof(a)
[1] "integer"

> a[0:5]
[1] 1 2 3 4 5

c (function): Combine Values Into A Vector Or List

Arrays

x <- 1:4
> is.array(x)
[1] FALSE
> x
[1] 1 2 3 4

> y <- array(1:4)
> y
[1] 1 2 3 4
> is.array(y)
[1] TRUE

Functions

fun = function(x) {
  x * x
}

> fun(3)
[1] 9

Control Flow

Conditional Statements

if (is.array(y)) {
    print(y)
}

Loops

arr <- 0  ## initialize
for (i in 1:5) {
    arr[i] <- i * i
}
print(arr)
[1]  1  4  9 16 25

Install & Import Libraries

## Install:
## 
install.packages('httr')

## Import into global namespace:
##
library(httr)

## Quantum random number generator :)
##
r <- httr::GET("https://qrng.anu.edu.au/ran_hex.php")

> typeof(r)
[1] "list"

> r$status_code
[1] 200

## response contains hex (8-bits)
##
> hex_str = content(r, "text")
> hex_str
[1] "e2"

> strtoi(hex_str, base=16)
[1] 226

Namespacing

> search()
 [1] ".GlobalEnv"        "package:httr"      "tools:rstudio"     "package:stats"    
 [5] "package:graphics"  "package:grDevices" "package:utils"     "package:datasets" 
 [9] "package:methods"   "Autoloads"         "package:base"

 ## Reference a specific package using ::
 ##
 httr::GET(...)

File Input / Output

> data <- read.csv('data/international-airline-passengers.csv' )# , header=TRUE, sep=",")
> typeof(data)
[1] "list"

Plotting

## https://www.tidyverse.org
##
install.packages('tidyverse')

ggplot2::ggplot(data=data.frame(data), ggplot2::aes(x=Month, y=passengers, group=1)) +
  ggplot2::geom_line()+
  ggplot2::geom_point()

Forecasting

install.packages('forecast')

library("magrittr")  ## for piping/chaining with %>%

## Seasonal ARIMA
##
data$passengers %>%
  arima(order=c(0,1,1), seasonal=c(0,1,1)) %>%
  residuals() %>%
  forecast::ggtsdisplay()

## Auto ARIMA
##
data$passengers %>%
  forecast::auto.arima() %>%
  residuals() %>%
  forecast::ggtsdisplay()

Miscellaneous

## Rename an attribute via names(...)
##
> names(data)
[1] "Month"
[2] "International.airline.passengers..monthly.totals.in.thousands..Jan.49...Dec.60"

> names(data)[names(data) == "International.airline.passengers..monthly.totals.in.thousands..Jan.49...Dec.60"] <- "Passengers"

> names(data)
[1] "Month"
[2] "Passengers"