The article is about R Quick Reference related to Data representation in R Language, Data Types in R, Checking/Testing of special values in R, Changing the basic data types, use of Mathem operations, rounding of the numbers and outputs, and mathematical functions.

### R Quick Reference

R language: A Quick Reference is about learning R Programming with a short description of the widely used commands. It will help the learner and intermediate user of the R Programming Language to get help with different functions quickly. This R Quick Reference is classified into different groups. Let us start with R Language: A Quick Reference – I.

### Basic Data Representation in R

In R, data may be represented as logical values, in scientific notation, as a `complex`

, or as a `float number`

. The are certain values such as `NA, NULL, NaN`

, and `Inf`

values.

R Command | Short Description |
---|---|

`True, False` | Logical true or false |

1.23e10 | A number in scientific notation $1.23\times 10^{20}$ |

3.4i | A complex number |

“Hello” | A String/ Characters |

NA | Missing Value representation (in any type of vector) |

NULL | Missing Value indicator in lists |

NaN | Not a number |

-Inf | Negative Infinity |

Inf | Positive infinity |

### Checking/ Testing the Basic Data Types in R

The type of data can be checked using some functions such as `is.logical(), is.numeric(), is.list(), is.character(), is.vector()`

or `is.complex()`

function.

R Command | Short Description |
---|---|

`is.logical(x)` | Results in true for logical vectors |

`is.numeric(x)` | Results in true for numeric vectors |

`is.character(x)` | Results in true for character vectors |

`is.list(x)` | Results in true for lists |

`is.vector(x)` | Results in true for both lists and vectors |

`is.complex(x)` | Results in true for complex vectors |

### Checking/ Testing the Special Values

The type of special values can be checked using `is.na(), is.nan(), is.finite(), is.ordered()`

, and `is.factor()`

etc., functions

R Command | Short Description |
---|---|

`is.na(x)` | Results in true for elements that are NA or NaN |

`is.nan(x)` | Results in true for elements that are NaN |

`is.null(x)` | Results in true whether $x$ is NULL |

`is.finite(x)` | Results in true for finite elements (e.g., not NA, NaN, Inf or -Inf) |

`is.infinite(x)` | Results in true for elements equal to Inf or -Inf |

`is.factor(x)` | Results in true for a factors and ordered factors |

`is.ordered(x)` | Results in true for ordered factors |

### Changing Basic Data Types in R

The Data Types in R can be changed by using functions such as, `as.logical(), as.numeric(), as.list()`

, or `as.numeric()`

etc., functions.

Type Coercion | Short Description |
---|---|

`as.logical(x)` | Coerces to a vector (However, lists remain lists) |

`as.numeric(x)` | Coerces a vector to a numeric vector |

`as.character(x)` | Coerces a vector to a character vector |

`as.list(x)` | Coerces a vector to a list |

`as.vector(x)` | Coerces to a vector (However, lists remains lists) |

`unlist(x)` | Converts a list to a vector |

`as.complex(x)` | Coerces to a vector (However, lists remain lists) |

### Basic Mathematical Operations

R can be used as a calculator. Mathematical operations such as addition, subtraction, multiplication, and division can also be performed.

Basic Math Operation | Short Description |
---|---|

x + y | Perform addition between the $x$ and $y$ vector |

x – y | Perform subtraction between the $x$ and $y$ vector |

x * y | Perform multiplication between the $x$ and $y$ vector |

x / y | Perform division between the $x$ and $y$ vector |

x ^ y | Perform exponentiation, “$x$ raised to power $y$” |

x %% y | Computes remainder, “$x$ modulo $y$” |

x %/% y | Performs Integer division, “$x$ divided by $y$”, discard the fractional part |

### Rounding off the Numbers

The numbers or values of a variable can be rounded as desired.

R Command | Short Description |
---|---|

round(x) | Round down the values of a variable to the next lowest integer |

`round(x, d)` | Round the values of a variable $x$ to the $d$ decimal places |

`signif(x, d)` | Round the values of a variable $x$ to $d$ significant digits |

`floor(x)` | Round down the values of a variable to next lowest integer |

`ceiling(x)` | Round up the values of a variable to the highest integer |

### Common Mathematical Functions

The commonly used mathematical functions in the R language are abs(), sqrt(), exp(), log(), and different bases of log functions.

R Command | Short Description |
---|---|

`abs(x)` | Absolute values |

`sqrt(x)` | Computes the square root of the values of a variable |

`exp(x)` | Computes $e^x$ |

`log(x)` | Computes the log values of the variable $x$ |

`log10(x)` | Computes the log base 10 (common log) of the variable $x$ |

`log2(x)` | Computes the log base 2 of the variable $x$ |

`log(x, base=b)` | Computes the log base $b$ of the variable $x$ |

### Trigonometric and Hyperbolic Functions

Following is the list of different trigonometric and Hyperbolic functions

Trigonometric Functions | Short Description |
---|---|

`sin(x), cos(x), tan(x)` | Computes the trigonometric values, sin, cos, and tan of a vector $x$ |

`asin(x), acos(x), atan(x)` | Computes the inverse trigonometric values of a vector $x$ |

`atan2(x, y)` | Computes arc tangent with two arguments |

`sinh(x), cosh(x), tanh(x)` | Computes hyperbolic values of a vector $x$ |

`asinh(x), acosh(x), atanh(x)` | Computes the inverse hyperbolic values of a vector $x$ |

### Special Mathematical Functions

The following is the list of special mathematical functions.

Mathematical Functions | Short Description |
---|---|

`beta(x, y)` | The beta function |

`lbeta(x, y)` | The log beta function |

`gamma(x)` | The gamma function |

`lgamma(x)` | The log gamma function |

`psigamma(x, deriv = 0)` | The psigamma function |

`digamma(x)` | The digamma function |

`trigamma(x)` | The trigamma function |