data_types_formats.qmd

# Data Types and Structures

```{r}
#| results: "asis"
#| echo: false
source("_common.R")
```

## Introduction

Like in Excel, data can be of different types.

## Data types

+------------------+---------------+-------------------------+----------------------+
| Type             | Short         | Description             | Example(s)           |
+==================+===============+=========================+======================+
| Numeric (double) | `<dbl>`       | Floating point number   | `3.14159`            |
+------------------+---------------+-------------------------+----------------------+
| Character        | `<char>`      | Character (text) string | `"S1P d18:1", "BQC"` |
+------------------+---------------+-------------------------+----------------------+
| Logical          | `<lgl>`       | True or False, 1 or 0   | `TRUE; FALSE`        |
+------------------+---------------+-------------------------+----------------------+
| Integer          | `<int>`       | Number without digits   | `3L; 7011L; -13L`    |
+------------------+---------------+-------------------------+----------------------+
| Factor           | `<fct>`       | Categorical data        | `BQC; TQC; SPL`      |
+------------------+---------------+-------------------------+----------------------+
| Date             | `<dt>`        | Date                    | `2022-01-31`         |
+------------------+---------------+-------------------------+----------------------+
| Time             | `<tm>`        | Time                    | `13:15; 1:15 pm`     |
+------------------+---------------+-------------------------+----------------------+
| Datetime         | `<dttm>`      | Date + Time             | `2022-01-31 13:15`   |
+------------------+---------------+-------------------------+----------------------+

## Type Conversions

+-------------+-------------------------------------------+---------------------------------------------------------------------------------------------------------+
| Type        | Functions                                 | Example(s)                                                                                              |
+=============+===========================================+=========================================================================================================+
| to Number   | `as.numeric()`                            | `as.numeric("3.14")`                                                                                    |
+-------------+-------------------------------------------+---------------------------------------------------------------------------------------------------------+
| to Text     | `as.character()`                          | `as.character(3.14)`                                                                                    |
+-------------+-------------------------------------------+---------------------------------------------------------------------------------------------------------+
| to Factor   | `factor()as.factor()forcats::as_factor()` | `as.factor(c("TQC", "SPL", "TQC")factor(  x = c("TQC", "SPL", "TQC"),   levels =  c("TQC", "SPL"` `) )` |
+-------------+-------------------------------------------+---------------------------------------------------------------------------------------------------------+
| to DateTime | `lubridate` package                       | `lubridate::as_datetime("31-12-2022 13:15")`                                                            |
+-------------+-------------------------------------------+---------------------------------------------------------------------------------------------------------+

## Data structures

+-------------+-----------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+
| Type        | Description                                                                 | Example(s)                                                                                |
+=============+=============================================================================+===========================================================================================+
| Vector      | Vector (series) of values. All values are of the same data type (see below) | `c(1,2,3,4)c("TQC", "BQC", "SPL")c(TRUE, FALSE)`                                          |
+-------------+-----------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+
| Matrix      | 2-dimensional set of values. All values are of the same data type           | `matrix(data = c(1:2),nrow = 2,ncol = 3)matrix(data = c("BQC", "SPL"),nrow = 2,ncol = 3)` |
+-------------+-----------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+
| Data Frame\ | Table with columns that can have different data types                       | `tibble(  No = c(1,2,3),   Sample = c("A", "B", "C"))`                                    |
| Tibble      |                                                                             |                                                                                           |
+-------------+-----------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+
| List        | Series of objects, that can be of different types, including e.g. tables    | `list(  Studysite = c("NUH", "SGH"),  Cohort = tibble(No = c(1,2),  Size = c(110,332)))`  |
+-------------+-----------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+

##