4 Data Structures
4.1 Data Types in R
Data types refer to the kind of data that can be stored and manipulated within a program. In R, the basic data types include:
- Numeric: Represents real numbers (e.g., 2, 15.5).
- Integer: Represents whole numbers (e.g., 2L, where L denotes an integer).
- Character: Represents strings (e.g., “hello”, “1234”). Character must be put between “.
- Logical: Represents Boolean values (TRUE or FALSE).
4.1.1 Assigning Values and Basic Operations
Assignment Operator
- The assignment operator in R is used to assign values to variables or objects in the R programming language.
- The leftwards assignment operator <-: This is the most commonly used assignment operator in R. It assigns the value on its right to the object on its left. For example, x <- 3 assigns the value 3 to the variable x.
- Alternative Assignment Operator (=) Apart from <-, R also supports the use of the = operator for assignments, similar to many other programming languages.
- However, the use of <- is preferred in R for historical and readability reasons. For example, x = 3 is valid but x <- 3 is more idiomatic to R.
Use <- or = for assigning values, e.g., x <- 10 or x= 10
Commenting Code for Clarity
Use # for comments, e.g., # This is a comment. - Comments are not executable and are used to provide relevant information about the syntax. Whatever is typed after # symbol, is considered as comment.
Arithmetic operators
- In R, arithmetic operators are used to perform common mathematical operations on numbers, vectors, matrices, and arrays. Here’s an overview of the primary arithmetic operators available in R:
+,-,*,/,^
Division (/) operator - Divides the first number or vector by the second, element-wise.
Square (^) operator - Squares the first number by the second.
4.2 Data Structures
Vectors
- Vectors are fundamental data structures that hold elements of the same type.
- They are one-dimensional arrays that can store numeric, character, or logical data.
- Assigning data to vectors in R is a basic operation, essential for data manipulation and analysis.
- The
c()function combines values into a vector. It’s the most common method for creating vectors.
Matrix
- A two-dimensional, rectangular collection of elements of the same type.
- All elements must be of the same data type.
- Created using the matrix() function. nrow is used to set number of rows and byrow is used to set values by rows (if TRUE) or columns (if FALSE).
Array
- Similar to matrices but can have more than two dimensions.
- Elements within an array must all be of the same data type.
- Created using the array() function. dimensions are set using dim.
Summary
| Concept | Description |
|---|---|
| Basic Data Types | |
| Numeric | Real numbers such as 2 or 15.5, the default numeric type in R |
| Integer | Whole numbers written with a trailing L, for example 2L, to distinguish them from numeric |
| Character | Strings of text enclosed in double quotes, for example "hello" or "1234" |
| Logical | Boolean values TRUE and FALSE used for conditions and logical comparisons |
| Assigning and Operating | |
| Assignment Operator | Uses `<-` or `=` to bind a value to a name, with `<-` preferred for idiomatic R code |
| Comments | Everything after the `#` symbol on a line is ignored by R, used to document intent |
| Arithmetic Operators | `+`, `-`, `*`, `/`, and `^` apply element-wise to numbers, vectors, matrices, and arrays |
| Data Structures | |
| Vector | One-dimensional sequence of values of the same type, created using the `c()` combine function |
| Matrix | Two-dimensional rectangular collection of same-type elements, created with the `matrix()` function and `nrow`, `ncol`, and `byrow` arguments |
| Array | Extends the matrix idea to three or more dimensions, created with the `array()` function using `dim` |