Base R Cheat Sheet

R is a free software enviro­nment for statis­tical computing and graphics.
It's a compiled language.
R is a dynami­cal­ly-­typ­ed,that means the type of a variable is determined at runtime, and that variables do not have to be explicitly declared with a specific type.
R is weakly­-typed, which means that it will automa­tically convert between types when necessary, without the need for explicit type casting.
R is a garbag­e-c­oll­ected language. This means the R runtime system automa­tically manages the memory used by the program.
R is both a functional an object oriented language but it doesn't support inheri­tance, polymo­rphism, and encaps­ula­tion.
In R, functions call by value. This means that when a function is called, the values of the arguments passed to the function are passed to the functi­on's local scope, and any changes made to the arguments within the function do not affect the original values of the arguments outside the function.

To code in R you can install the extension in your IDE like VSC or install its own IDE R Studio :
R for Windows
R for Linux
Then to run it you can run it with the IDE if you don't have one you can use R Studio server, which is a web-based version of R Studio that can be accessed through a web browser. The command for R Studio is Rscript myscript.R .
When installed R Studio it would have a minimal impact impact on the local machine but if you runs large R scripts or using R for data analysis and machine learning tasks, which require a lot of memory,it may have a bigger impact on the local machine. But in the end it does not modify something in your machine that would block you in it's use.

Code
instal­l.p­ack­age­s('d­ply­r') : Download and install a package from CRAN.
librar­y(d­ply­r') : Load the package into the file.
dplyr:­:select : Use a function from the package

Commonly used library
stringr for string manipu­lation
dplyr for data frame manipu­lation
ggplot2 for plotting graphs
lubridate for date

R is an integrated suite of software facilities for data manipu­lation, calcul­ation and graphical display. It includes:
-An effective data handling and storage facility,
-A suite of operators for calcul­ations on arrays, in particular matrices,
-A large, coherent, integrated collection of interm­ediate tools for data analysis,
-Graphical facilities for data analysis and display either on-screen or on hardcopy, and
-A well-d­eve­loped, simple and effective progra­mming language which includes condit­ionals, loops, user-d­efined recursive functions and input and output facili­ties.
The people who mainly use R are data scientist / engineer

Variable Assignment
a <- '­bon­jou­r' : string
a <- 6 : integer

Loop
For loop :
for (variable in sequence){ Do something }
While loop :
while (condi­tion){ Do something }

Condition
if (condi­tion){ Do something } else { Do something different }
a == b : Are equal
a > b : Greater than
a >= b : Greater than or equal to
is.na(a) : Is missing
a != b : Not equal
a < b : Less than
a <= b : Less than or equal to
is.null(a) : Is null

Functions
functi­on_name <- function (var){ Do something return (new_v­ari­able) }

Maths Functions
log(x) : Natural log / sum(x) : Sum
exp(x) : Expone­ntial / mean(x) : Mean
max(x) : Largest element / median(x) : Median
min(x) : Smallest element / quanti­le(x) : Percentage quantiles
round(x, n) : Round to n decimal places
rank(x) : Rank of elements
signif(x, n) : Round to n signif­icant figures
var(x) : The variance / cor(x, y) : Correl­ation
sd(x) : The standard deviation

Lists
l <- list(x = 1:5, y = c('a­', '­b')) : A list is collection of elements which can be of different types.
l[[2]] : second element of l
l[1] : new list with only the first element
l$x : element named x
l['y­'] : new list with only element named y

String
paste(x, y, sep = ' ') : Join multiple vectors together.
paste(x, collapse = ' ') : Join elements of a vector together.
grep(p­attern, x) : Find regular expression matches in x.
gsub(p­attern, replace, x) : Replace matches in x with a string.
toupper(x) : Convert to uppercase.
tolower(x) : Convert to lowercase.
nchar(x) : Number of characters in a string.

Matrixes
m <- matrix(x, nrow = 3, ncol = 3) : Create a matrix from x.
df[ , 2] : Select a column .
df[2, ] : Select a row.
df[2, 2] : Select an element.


Data Frames
df <- data.f­rame(x = 1:3, y = c('a­', '­b', '­c')) : A special case of a list where all elements are the same length.
View(df) : See the full data frame.
head(df) :See the first 6 rows.
nrow(df) : Number of rows.
ncol(df) : Number of columns.
dim(df) : Number of columns and rows.
As the same sub settings as matrixes and lists

Ploting
plot(x) : plot values of x in order
plot(x, y) : plot values of x against y

Reading and writing data
df <- read.t­abl­e('f­ile.tx­t') / df <- read.c­sv(­'­fil­e.c­sv') / Read a file text or a csv
write.t­ab­le(df, ‘file.t­xt’) / write.c­sv(df, ‘file.c­sv’) / Write a file text or a csv