Лабораторное занятие № 2. Презентация

Vasily V. Grinev. Introduction to R Programming
LIST OF PRACTICAL TASKS
Task by task.
Task #6: Development a multi-component R command.
Task #7: Handling with character constants.
Task #8: Handling with numeric constants.
Task #9: Handling with built-in constants.
Task #10: Using operators.
Task #11: Using built-in functions.
Duration.
Eighty minutes (in total) per group of students.

Components of R commands:
constants;
variabilities;
operators;
functions;
control structures.
PRACTICAL TASK #6:
Development a multi-component R command
When completing the first task, you must create a multi-component R command that would include constant(-s), variability(-ies), operator(-s)
and function(-s).
Vasily V. Grinev. Introduction to R Programming
See videolecture “Videolecture #2.1. How R works” at YouTube hosted Grinev's Educational Channel
https://www.youtube.com/watch?v=4bsf23GKy8c
for future details.
> paste("A circle with a diameter of", 5, "cm", "has circumference",
+ round(pi * 5, digits=3), "cm")

Vasily V. Grinev. Introduction to R Programming
A constant is entity whose value(-s) cannot be altered.
A variable is an object used to store data whose value(-s) can be changed
if necessary.
There are built-in and user-defined constants. Basic classes of constants are character constants and numeric constants.
Character constants can be represented using either single quotes (') or double quotes (") as delimiters.
> "example"
[1] "example"
> typeof(x="example")
[1] "character"
Basic definitions
PRACTICAL TASK #7: Handling with character constants

Vasily V. Grinev. Introduction to R Programming
Creating a character constant:
Task content
PRACTICAL TASK #7: Handling with character constants
> "example"
[1] "example“
> con <- "example"
> con
[1] "example"
Replacement of constant:
> con1 <- "blood"
> con1
[1] "blood"
> con2 <- sub(pattern="loo", replacement="rea", x=con1)
> con2
[1] "bread"

Vasily V. Grinev. Introduction to R Programming
Concatenation of character strings:
Task content
PRACTICAL TASK #7: Handling with character constants
> con1 <- "I"
> con2 <- "love"
> con3 <- "R"
> con <- paste(con1, con2, con3, sep=" ")
> con
[1] "I love R"
> con <- paste("I", "love", "R", sep=" ")
> con
[1] "I love R"
Splitting of character string:
> con <- paste("I", "love", "R", sep=" ")
> con
[1] "I love R"
> strsplit(x=con, split=" ")[[1]]
[1] "I" "love" "R"

Vasily V. Grinev. Introduction to R Programming
Numeric constants belong to three types:
integer (integer numbers)
> 4L
[1] 4
> typeof(x=4L)
[1] "integer"
double (double precision floating point numbers)
> 4.5
[1] 4.5
> typeof(x=4.5)
[1] "double"
complex (complex numbers)
> 4.5i
[1] 0+4.5i
> typeof(x=4i)
[1] "complex"
PRACTICAL TASK #8: Handling with numeric constants
Basic definitions

Vasily V. Grinev. Introduction to R Programming
Creating an integer constant:
Task content
### by appending an L suffix
> con <- 5L
> con
[1] 5
### by function as.integer()
> con <- as.integer(x=5)
> con
[1] 5
> as.integer(x=5.4)
[1] 5
> as.integer(x="5.4")
[1] 5
> as.integer(x="love")
[1] NA
Warning message:
NAs introduced by coercion
PRACTICAL TASK #8: Handling with numeric constants

Vasily V. Grinev. Introduction to R Programming
Inspection a type and/or class of integer constant:
Task content
> con <- 5L
### by function typeof()
> typeof(x=con)
[1] "integer"
### by function class()
> class(x=con)
[1] "integer“
### by function is.integer()
> is.integer(x=con)
[1] TRUE
PRACTICAL TASK #8: Handling with numeric constants

Vasily V. Grinev. Introduction to R Programming
The reasons for existing integer constants:
The integer is represented explicitly. At the same time, the representing real numbers always involves an approximation and a potential loss of significant digits.
Testing for the equality of two real numbers is not a realistic way to think when dealing with the numbers in a computer. Direct comparison of real numbers can cause errors.
Performing arithmetic on very small or very large real numbers can lead to errors that are not possible in abstract mathematics.
The more bits we use to represent a real number, the greater the precision of the representation and the more memory we consume.
### memory allocation
> object.size(x=1:100)
448 bytes
> object.size(x=as.numeric(x=1:100))
848 bytes
Task content
PRACTICAL TASK #8: Handling with numeric constants

Vasily V. Grinev. Introduction to R Programming
There are several built-in constants:
The 26 upper-case letters of the Roman alphabet
> LETTERS
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q"
[18] "R" "S" "T" "U" "V" "W" "X" "Y" "Z"
The 26 lower-case letters of the Roman alphabet
> letters
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" "t"
[21] "u" "v" "w" "x" "y" "z"
The English names for the months of the year
> month.name
[1] "January" "February" "March" "April" "May" "June" "July" "August"
[9] "September" "October" "November" "December"
The three-letter abbreviations for the English month names
> month.abb
[1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct"
[11] "Nov" "Dec"
The ratio of the circumference of a circle to its diameter
> pi
[1] 3.141593
PRACTICAL TASK #9: Handling with built-in constants
Basic definitions

Vasily V. Grinev. Introduction to R Programming
Some manipulations with character built-in constants:
Task content
> LETTERS
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T"
[20] "T" "U" "V" "W" "X" "Y" "Z"
> tolower(x=LETTERS)
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" "t" "u" "v“
[23] "w" "x" "y" "z"
> toupper(x=letters)
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T"
[20] "T" "U" "V" "W" "X" "Y" "Z"
PRACTICAL TASK #9: Handling with built-in constants
> month.name
[1] "January" "February" "March" "April" "May" "June" "July" "August"
[9] "September" "October" "November" "December“
> substr(x=month.name, start=1, stop=3)
[1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"

Vasily V. Grinev. Introduction to R Programming
There are several special built-in constants:
Infinity
> Inf
[1] Inf
Not Available; it is used to indicate missing values in the data
> NA
[1] NA
Not A Number; it indicates an undefined number or "not a number"
> NaN
[1] NaN
A null object; it is often used when the return value of an expression or function is not defined
> NULL
NULL
PRACTICAL TASK #9: Handling with built-in constants
Basic definitions

Vasily V. Grinev. Introduction to R Programming
Some manipulations with special built-in constants:
Task content
> v <- 4:13
> v
[1] 4 5 6 7 8 9 10 11 12 13
> v[c(2, 4, 7)] <- c(5/0, NA, NaN)
> v
[1] 4 Inf 6 NA 8 9 NaN 11 12 13
PRACTICAL TASK #9: Handling with built-in constants
> is.na(x=v)
[1] FALSE FALSE FALSE TRUE FALSE FALSE TRUE FALSE FALSE FALSE
> is.nan(x=v)
[1] FALSE FALSE FALSE FALSE FALSE FALSE TRUE FALSE FALSE FALSE
> is.finite(x=v)
[1] TRUE FALSE TRUE FALSE TRUE TRUE FALSE TRUE TRUE TRUE
> is.infinite(x=v)
[1] FALSE TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
> table(is.infinite(v))
FALSE TRUE
9 1

In any programming language, an operator is a symbol that tells the compiler or interpreter to perform specific operation and produce final result.
Type (category) of operators in R:
arithmetic operators;
relational operators;
logical operators;
assignment operators;
miscellaneous operators.
You can get help about any operator via ?"operator_name".
Vasily V. Grinev. Introduction to R Programming
For future reading:
1) Operator (computer programming) (https://en.wikipedia.org/wiki/Operator_(computer_programming))
2) Basics of operators (https://www.hackerearth.com/ru/practice/basic-programming/operators)
3) R operators (https://www.datamentor.io/r-programming/operator)
4) R-operators (https://www.tutorialspoint.com/r/r_operators.htm)
5) Operators in C/C++ (https://www.geeksforgeeks.org/operators-c-c/)
6) Java - Basic operators (https://www.tutorialspoint.com/java/java_basic_operators.htm)
PRACTICAL TASK #10: Using operators
Basic definitions

R arithmetic operators
Vasily V. Grinev. Introduction to R Programming
These operators perform standard arithmetic operations with each element of the vector.
PRACTICAL TASK #10: Using operators

R relational operators
Vasily V. Grinev. Introduction to R Programming
Each element of the first vector is compared with the corresponding element of the second vector. The result of comparison is a Boolean value.
PRACTICAL TASK #10: Using operators

R logical operators
Vasily V. Grinev. Introduction to R Programming
It is applicable to logical, numeric or complex vectors. Each element of the first vector is compared with the corresponding element of the second vector. The result of comparison is a Boolean value. The logical operator && and || considers the first element of the vectors and give a single element output.
PRACTICAL TASK #10: Using operators

R assignment operators
Vasily V. Grinev. Introduction to R Programming
These operators are used to assign values to variables. The operators <- and = can be used to assign to variable in the same environment. The <<- operator is used for assigning to variables in the parent environments.
PRACTICAL TASK #10: Using operators

R miscellaneous operators
Vasily V. Grinev. Introduction to R Programming
These operators are used for specific purposes and not general arithmetic or logical computation.
PRACTICAL TASK #10: Using operators

R miscellaneous operators
Vasily V. Grinev. Introduction to R Programming
PRACTICAL TASK #10: Using operators

Vasily V. Grinev. Introduction to R Programming
Practice with all main R operators. Use the true data sets.
Task content
> v <- 4:13
> v
[1] 4 5 6 7 8 9 10 11 12 13
> v + 1
[1] 5 6 7 8 9 10 11 12 13 14
PRACTICAL TASK #10: Using operators

Built-in function is a function which already created or defined in the programming framework.
Built-in functions in R:
math, or numeric, functions;
character, or string, functions;
basic statistical functions;
statistical probability functions;
other functions.
You can get help about any built-in function via ?function_name.
Vasily V. Grinev. Introduction to R Programming
See videolecture “Videolecture #9.1. Introduction in R functions” at YouTube hosted Grinev's Educational Channel https://www.youtube.com/watch?v=Lf-B4fNXm1g&t=696s
for future details.
PRACTICAL TASK #11: Using built-in functions
Basic definitions

R math functions
Vasily V. Grinev. Introduction to R Programming
PRACTICAL TASK #11: Using built-in functions

R character functions
Vasily V. Grinev. Introduction to R Programming
PRACTICAL TASK #11: Using built-in functions

R basic statistical functions
Vasily V. Grinev. Introduction to R Programming
PRACTICAL TASK #11: Using built-in functions

Vasily V. Grinev. Introduction to R Programming
Practice with all main R built-in functions. Use the true data sets.
Task content
> v <- 4:13
> v
[1] 4 5 6 7 8 9 10 11 12 13
> sqrt(x=v)
[1] 2.00000 2.23607 2.44949 2.64575 2.82843 3.00000 3.16228 3.31662
[9] 3.46410 3.60555
PRACTICAL TASK #11: Using built-in functions