---
title: "Glossary of REDCap and REDCapTidieR Terms"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Glossary of REDCap and REDCapTidieR Terms}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r setup, include = FALSE}
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
```

The REDCapTidieR package uses vocabulary that is standard for REDCap database architects but not necessarily well known to all R users. It also introduces several idiosyncratic terms.

Below we provide a rough mapping of REDCap concepts to their corresponding artifacts in REDCapTidieR. This is followed by a listing of term definitions.

+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| REDCap                                     | REDCapTidieR                                                                                             |
+:==========================================:+:========================================================================================================:+
| [Project](#project), Database              | [Supertibble](#supertibble)                                                                              |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Instrument](#instrument), Form            | One [row](#row) of the [supertibble](#supertibble)                                                       |
|                                            |                                                                                                          |
|                                            | Data is in the [data tibble](#data-tibble)                                                               |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Field](#field)                            | [Data column](#data-column) (a [column](#column) of the [data tibble](#data-tibble))                     |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Field](#field) name                       | [Variable](#variable) name of a [data column](#data-column)                                              |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Field type](#field-type)                  | Data type of a [data column](#data-column)                                                               |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Field label](#field-label)                | [Variable label](#variable-label) of a [data column](#data-column)                                       |
|                                            |                                                                                                          |
|                                            | (only present if [supertibble](#supertibble) is [labelled](#labelled))                                   |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Record](#record)                          | One or several [rows](#row) of a [data tibble](#data-tibble)                                             |
|                                            |                                                                                                          |
|                                            | Record ID [column](#column) is the first column of a [data tibble](#data-tibble)                         |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Event](#event)                            | `redcap_event` [column](#column) of a [data tibble](#data-tibble)                                        |
|                                            |                                                                                                          |
|                                            | (only present if the [project](#project) is [longitudinal](#longitudinal-project))                       |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Arm](#arm)                                | `redcap_arm` [column](#column) of a [data tibble](#data-tibble)                                          |
|                                            |                                                                                                          |
|                                            | (only present if the [project](#project) is [longitudinal](#longitudinal-project) with multiple arms)    |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Repeat Instrument](#repeating-instrument) | `redcap_form_instance` [column](#column) of a [data tibble](#data-tibble)                                |
|                                            |                                                                                                          |
|                                            | (only present if the [instrument](#instrument) is [repeating](#repeating-instrument))                    |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Repeat Event](#repeating-event)           | `redcap_event_instance` [column](#column) of a [data tibble](#data-tibble)                               |
|                                            |                                                                                                          |
|                                            | (only present if the [instrument](#instrument) is associated with a [repeating event](#repeating-event)) |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+
| [Data Access Group](#data-access-group)    | `redcap_data_access_group` [column](#column) of a [data tibble](#data-tibble)                            |
|                                            |                                                                                                          |
|                                            | (only present if the [project](#project) has [data access groups](#data-access-group) enabled)           |
+--------------------------------------------+----------------------------------------------------------------------------------------------------------+

### Arm {#arm}

An ordered group of [events](#event). Arms provide a mechanism that allows one [longitudinal project](#longitudinal-project) to have multiple different sequences of events defined. <a onclick="history.back()">↩︎</a>

### Block matrix {#block-matrix}

A rectangular data structure (matrix) that is constructed from multiple smaller rectangular data structures (blocks). In the context of REDCap, the block matrix is the rectangular data set that contains data from multiple [instruments](#instrument) returned by the [REDCap API](#redcap-api). <a onclick="history.back()">↩︎</a>

### Column {#column}

A vertical series of cells in a data frame or [tibble](#tibble). Synonym: [Variable](#variable). See also: [Row](#row). <a onclick="history.back()">↩︎</a>

### Composite primary key {#composite-primary-key}

A primary key is a [column](#column) in a table that is distinct in each [row](#row) and serves to identify each row. A composite primary key is a primary key that consists of multiple columns that in combination are distinct in each row and serve to identify each row. Taken together, the [identifier columns](#identifier-column) of the [data tibble](#data-tibble) form a composite primary key. This makes it easy to join data tibbles together. <a onclick="history.back()">↩︎</a>

### Choice {#choice}

An option or category defined in the context of a single-answer or multi-answer categorical [field type](#field-type) in REDCap. You can define choices using the REDCap Field Editor. Choices have a **raw value** (a unique identifier - usually a serial number but this can be changed) and a **choice label** (a human readable description of the choice, which is displayed during data entry).

In the context of REDCapTidieR, choices come into play in two scenarios during the construction of the [data tibble](#data-tibble). Choice labels of single-answer type [fields](#field) (dropdown and radio) are used to define the values of [data columns](#data-column) that are derived from those fields. Raw values of the multi-answer checkbox field are used to construct the names of data columns derived from them. <a onclick="history.back()">↩︎</a>

### Classic project {#classic-project}

Also known as a **traditional** project, this the simplest type of REDCap [project](#project). You can define one or multiple [instruments](#instrument) (also called forms) for data entry. Both [repeating](#repeating-instrument) and [nonrepeating](#repeating-instrument) instruments are allowed. Nonrepeating instruments are completed only once for each [record](#record). For nonrepeating instruments, one [row](#row) of data in the [data tibble](#data-tibble) represents one record. Repeating instruments can be completed an arbitrary number of times for each record. For repeating instruments, one row of data in the data tibble represents one repeat instance of one record. See also: [Longitudinal project](#longitudinal-project). <a onclick="history.back()">↩︎</a>

### Data Access Group {#data-access-group}

The Data Access Group (DAG) feature of REDCap streamlines multi-group collaboration by partitioning groups of [records](#record) of a single [project](#project). This feature is particularly useful when you want certain users or groups of users to only have access to a specific subset of the data in a project.

In a multi-site study, for instance, you might want each site to only have access to their own data. By setting up a DAG for each site, you can ensure that site users can only view and edit records that belong to their DAG. Super users (i.e., those with full privileges) can view and edit all records in the project, regardless of the DAG to which they belong. 

When a [project](#project) has DAGs enabled, a corresponding `redcap_data_access_group` [column](#column) identifies which DAG a given [record](#record) belongs to. 

### Database {#database}

In the context of REDCap, this is the same as [project](#project). We prefer the term "project" because it is has a more specific meaning. <a onclick="history.back()">↩︎</a>

### Data column {#data-column}

A [column](#column) of the [data tibble](#data-tibble) that is derived from data that were entered into the [fields](#field) of a REDCap [instrument](#instrument). <a onclick="history.back()">↩︎</a>

### Data tibble {#data-tibble}

A [tibble](#tibble) that contains data that were entered into the [fields](#field) of a specific REDCap [instrument](#instrument). The `redcap_data` column of the [supertibble](#supertibble) contains the data tibbles of a [project](#project). The columns of the data tibble include [identifier columns](#identifier-column) that jointly identify each row and [data columns](#data-column) that contain data that was entered into REDCap. REDCapTidieR provides several functions to extract data tibbles from the supertibble. See also: [Metadata tibble](#metadata-tibble). <a onclick="history.back()">↩︎</a>

### Data viewer {#data-viewer}

A part of the [RStudio IDE](https://posit.co/download/rstudio-desktop) functionality that allows you to inspect data frames, [tibbles](#tibble), and some other data structures. It includes [features to perform basic exploratory data analysis](https://docs.posit.co/ide/user/ide/guide/data/data-viewer.html) such as sorting, filtering, and searching. [The supertibble is designed to work well with the data viewer](REDCapTidieR.html#exploring-the-contents-of-the-supertibble). <a onclick="history.back()">↩︎</a>

### Environment {#environment}

A fundamental data structure in R that allows **binding** a set of names to a set of objects. The **global environment** is the namespace in which you bind objects such as values and [tibbles](#tibble) during interactive work. The `bind_tibbles()` function takes a [supertibble](#supertibble) and binds its [data tibbles](#data-tibble) to the global environment. <a onclick="history.back()">↩︎</a>

### Event {#event}

A part of a [longitudinal project](#longitudinal-project). Each event can be associated with one or multiple [instruments](#instrument) and may be either [repeating](#repeating-event) or [nonrepeating](#nonrepeating-event). <a onclick="history.back()">↩︎</a>

### Factor variable {#factor}

A data type in R for categorical data. By default, single-answer categorical REDCap [field types](#field-type) (dropdown, radio) are represented as factor variables in the [data tibble](#data-tibble). <a onclick="history.back()">↩︎</a>

### Field {#field}

An attribute about an entity (e.g., age or height) that can be captured in REDCap. [Instruments](#instrument) are made up of fields. You can configure the fields of an instrument using the REDCap Field Editor. Fields have a [field type](#field-type) and can have a descriptive [field label](#field-label). The [data tibble](#data-tibble) contains the data entered into the fields of a REDCap [project](#project). <a onclick="history.back()">↩︎</a>

### Field label {#field-label}

A piece of text that acts as the prompt for data entry in REDCap. The `make_labelled()` function creates [variable labels](#variable-label) based on the field label. <a onclick="history.back()">↩︎</a>

### Field type {#field-type}

The data type of the data that can be entered into a specific field. Important field types include:

-   **text**, which is used for free-text and numeric data

-   **yesno** and **truefalse**, which are used for logical data

-   **dropdown** and **radio**, which are used for single-answer categorical data

-   **checkbox**, which is used for multi-answer categorical data
 <a onclick="history.back()">↩︎</a>

### Form

In the context of REDCap, this is the same as an [instrument](#instrument). We prefer the term "instrument" because it has a more specific meaning than "form." <a onclick="history.back()">↩︎</a>

### Format helper {#format-helper}

A function provided by REDCapTidieR designed to help turning [field labels](#field-label) of [data columns](#data-column) into pretty [variable labels](#variable-label). See [`format-helpers`](https://chop-cgtinformatics.github.io/REDCapTidieR/reference/format-helpers.html). <a onclick="history.back()">↩︎</a>

### Granularity {#granularity}

The level of detail that a specific [row](#row) in a [data tibble](#data-tibble) represents. This depends on the [structure](#structure) of the [project](#project) ([classic](#classic-project) vs. [longitudinal](#longitudinal-project) vs. longitudinal with [arms](#arm)), the structure of the [instrument](#instrument) ([repeating](#repeating-instrument) vs. [nonrepeating](#nonrepeating-instrument)), and, for longitudinal projects, the structure of the [event](#event) ([repeating](#repeating-event) vs. [nonrepeating](#nonrepeating-event)). For example, a data tibble containing data from a nonrepeating instrument in a longitudinal project with two arms has a granularity of one row per [record](#record) per [event](#event) per arm. See also: the section [Longitudinal REDCap projects](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html#longitudinal-redcap-projects) in the [Diving Deeper vignette](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html). <a onclick="history.back()">↩︎</a>

### Identifier column {#identifier-column}

A [column](#column) in the [data tibble](#data-tibble) that serves to partially identify the entity described in a [row](#row). The [record](#record) ID column is always present in the data tibble. Depending on the [structure](#structure) of the [project](#project) ([classic](#classic-project) vs. [longitudinal](#longitudinal-project) vs. longitudinal with [arms](#arm)), the structure of the [instrument](#instrument) ([nonrepeating](#nonrepeating-instrument) vs [repeating](#repeating-instrument)), and the structure of the [event](#event) ([repeating](#repeating-event) vs. [nonrepeating](#nonrepeating-event)) there may be additional identifier columns, including `redcap_event`, `redcap_arm`, `redcap_form_instance`, and `redcap_event_instance`. Taken together, the identifier columns form a [composite primary key](#composite-primary-key). See also: the section [Longitudinal REDCap projects](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html#longitudinal-redcap-projects) in the [Diving Deeper vignette](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html). <a onclick="history.back()">↩︎</a>

### Import {#import}

In the context of REDCapTidieR, this is the process of using the [REDCap API](#redcap-api) to query data from a REDCap [project](#project) to make it available inside the R [environment](#environment). We use the term "import" in the sense described in [R for Data Science](https://r4ds.had.co.nz/introduction.html) which is to "take data stored in a file, database, or web application programming interface (API), and load it into a data frame in R." Of note, the term "import" is ambiguous. From the perspective of REDCap, "import" may mean writing external data into the database. To clarify the direction of the import, we have named the main function of REDCapTidieR `read_redcap()` which is analogous to other import functions in the tidyverse such as `read_csv()`. You can use the `read_redcap()` function to import data from a REDCap project. <a onclick="history.back()">↩︎</a>

### Instrument {#instrument}

Also called **form**. An electronic data entry form in REDCap. An instrument contains [fields](#field) into which data can be entered. In the [supertibble](#supertibble), each [row](#row) corresponds to one instrument. The instrument's name and human-readable label are shown in the `redcap_form_name` and `redcap_form_label` columns of the supertibble, respectively. A [data tibble](#data-tibble) contains all the data that was entered into a specific instrument. <a onclick="history.back()">↩︎</a>

### labelled {#labelled}

The [labelled](https://larmarange.github.io/labelled/) R package provides functions to attach a human-readable description (a label) to a [variable](#variable) (a [variable label](#variable-label)). Labelled data can streamline data exploration and assist with the generation of a data dictionary. There are [multiple](https://jonocarroll.github.io/ggeasy/) [packages](https://www.danieldsjoberg.com/gtsummary/) [that](https://github.com/pcctc/croquet) [support](https://strengejacke.github.io/sjlabelled/index.html) [labelled](https://larmarange.github.io/labelled/) [data](https://haven.tidyverse.org/reference/labelled.html). The `make_labelled()` function attaches variable labels to the variables of a [supertibble](#supertibble) and the variables of the [data tibbles](#data-tibble) and [metadata tibbles](#metadata-tibble) contained in that supertibble. <a onclick="history.back()">↩︎</a>

### List column

A [list](https://r4ds.had.co.nz/vectors.html#lists) is a fundamental data type in R. A [tibble](#tibble) can contain [columns](#column) that are lists, and these columns are called [list columns](https://r4ds.hadley.nz/rectangling.html#list-columns). REDCapTidieR leverages list columns to store tibbles inside of the [supertibble](#supertibble). For example, the `redcap_data` column of the supertibble is a list column that contains [data tibbles](#data-tibble), and `redcap_metadata` is a list column that contains [metadata tibbles](#metadata-tibble). <a onclick="history.back()">↩︎</a>

### Longitudinal project {#longitudinal-project}

A type of REDCap [project](#project) that contains [events](#event) and optionally [arms](#arm). One [instrument](#instrument) can be associated with multiple events. This makes it possible to collect the same kind of data for the same [record](#record) multiple times, which is useful for longitudinal research studies with multiple study visits. See also: [Classic project](#classic-project). <a onclick="history.back()">↩︎</a>

### Metadata tibble {#metadata-tibble}

A [tibble](#tibble) that contains metadata about a specific REDCap [instrument](#instrument). The `redcap_metadata` [column](#column) of the [supertibble](#supertibble) contains the metadata tibbles of a [project](#project). The rows of the metadata tibble represent [fields](#field) of the instrument. The columns represent attributes of those fields. For example, the `field_name`, `field_label`, and `field_type` columns show the field's name, a human-readable description (the [field label](#field-label)), and its [field type](#field-type). <a onclick="history.back()">↩︎</a>

### Nonrepeating Event {#nonrepeating-event}

An [event](#event) whose associated [instruments](#instrument) can be filled out exactly once per record per event (and per [arm](#arm), if applicable). See also: [Repeating Event](#repeating-event). <a onclick="history.back()">↩︎</a>

### Nonrepeating Instrument {#nonrepeating-instrument}

An [instrument](#instrument) that can be filled out exactly once per [record](#record) in a [classic project](#classic-project) and once per record per [event](#event) instance (and per [arm](#arm), if applicable) in a [longitudinal project](#longitudinal-project). See also: [Repeating Instrument](#repeating-instrument). <a onclick="history.back()">↩︎</a>

### Project {#project}

Also called a **database**, a REDCap project is a self-contained collection of all the of data and metadata related to some data collection activity (for example, a specific research study). A project may be [classic](#classic-project) or [longitudinal](#longitudinal-project). A classic project consists of [instruments](#instrument) that contain [fields](#field). A longitudinal project may additionally include [events](#event) and [arms](#arm). You can use `read_redcap()` to [import](#import) the data from a project. <a onclick="history.back()">↩︎</a>

### Record {#record}

The set of information about a single entity (e.g., a study participant) for which data is being captured in a specific REDCap [project](#project). Each record consists of a discrete data values organized into [fields](#field) that can be spread across multiple [instruments](#instrument), [events](#event), and/or [arms](#arm). Each record has a unique record ID. In the [data tibble](#data-tibble), the record ID is always the first [column](#column). The record ID column is one of the [identifier columns](#identifier-column). <a onclick="history.back()">↩︎</a>

### REDCap API {#redcap-api}

The application programming interface (API) of a REDCap instance allows external programs to connect, upload, and download data. To access the REDCap API, a user must have appropriate access privileges, an API token, and the uniform resource identifier (URI) of the API endpoint (something like "my.institution.edu/redcap/api"). The REDCapTidieR package uses [REDCapR](#redcapr) to query the REDCap API. <a onclick="history.back()">↩︎</a>

### REDCapR {#redcapr}

The [REDCapR](https://ouhscbbmc.github.io/REDCapR/index.html) R package provides functions to interact with the [REDCap API](#redcap-api). REDCapTidieR builds on REDCapR to [import](#import) data into R. <a onclick="history.back()">↩︎</a>

### Repeating Event {#repeating-event}

An [event](#event) whose associated [instruments](#instrument) can be filled out zero, one, or multiple times per record per event (and per [arm](#arm), if applicable). Note: REDCap does not allow [repeating instruments](#repeating-instrument) inside repeating events. See also: [Nonrepeating Event](#nonrepeating-event). <a onclick="history.back()">↩︎</a>

### Repeating Instrument {#repeating-instrument}

An [instrument](#instrument) that can be filled out zero, one, or multiple times per [record](#record) in a [classic project](#classic-project) and zero, one, or multiple times per record per [event](#event) (and per [arm](#arm), if applicable) in a [longitudinal project](#longitudinal-project). Note: REDCap does not allow repeating instruments inside [repeating events](#repeating-event). See also: [Nonrepeating Instrument](#nonrepeating-instrument). <a onclick="history.back()">↩︎</a>

### Row {#row}

A horizontal series of cells in a data frame or [tibble](#tibble). One row of a [supertibble](#supertibble) represents an [instrument](#instrument). One row of a [data tibble](#data-tibble) can represent different things, depending on the [granularity](#granularity) of the data. See also: [Column](#column). <a onclick="history.back()">↩︎</a>

### skimr {#skimr}

The [skimr](https://docs.ropensci.org/skimr/) R package provides summary statistics to help users quickly skim and understand their data. REDCapTidieR's `add_skimr_metadata()` function uses [skimr](https://docs.ropensci.org/skimr/) to add various summary statistics of a specific [field](#field) to the [metadata tibbles](#metadata-tibble). See also: the section [Adding summary statistics to the metadata with the skimr package](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/REDCapTidieR.html#adding-summary-statistics-to-the-metadata-with-the-skimr-package) in the [Getting Started vignette](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/REDCapTidieR.html).

### Structure {#structure}

The structure of an [instrument](#instrument) can be [repeating](#repeating-instrument), [nonrepeating](#nonrepeating-instrument), or mixed. The [supertibble](#supertibble) shows the instrument's structure in the `structure` column. The structure of a [project](#project) can be [classic](#classic-project), [longitudinal](#longitudinal-project), or longitudinal with [arms](#arm). The structure of an [event](#event) can be [repeating](#repeating-event) or [nonrepeating](#nonrepeating-event). As of REDCapTidieR v1.1.0, [mixed structure instruments](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html#mixed-structure-instruments) are supported. The [granularity](#granularity) of a [data tibble](#data-tibble) depends on the structure of all three: the instrument, the project, and the events associated with the instrument. Note: REDCap does not allow repeating instruments inside a repeating event. See also: the section [Longitudinal REDCap projects](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html#longitudinal-redcap-projects) in the [Diving Deeper vignette](https://chop-cgtinformatics.github.io/REDCapTidieR/articles/diving_deeper.html). <a onclick="history.back()">↩︎</a>

### Supertibble {#supertibble}

A special [tibble](#tibble) that contains data and metadata of a REDCap [project](#project) returned by the `read_redcap()` function. Each [row](#row) of the supertibble corresponds to one [instrument](#instrument). The `redcap_form_name` and `redcap_form_label` [columns](#column) identify the instrument. The `redcap_data` and `redcap_metadata` contain the instrument's [data tibble](#data-tibble) and [metadata tibble](#metadata-tibble). Additional columns contain useful information about the data tibble, such as row and column counts, size in memory, and the percentage of missing values in the data. <a onclick="history.back()">↩︎</a>

### Survey {#survey}

A special kind of [instrument](#instrument) that can be completed by someone who is not a user on a REDCap [project](#project). <a onclick="history.back()">↩︎</a>

### Tibble {#tibble}

A variant of the R data frame that makes data analysis in the [tidyverse](https://tidyverse.org/) a little easier. The data structures generated by REDCapTidieR are based on tibbles. See also: chapter on [Tibbles](https://r4ds.had.co.nz/tibbles.html) in [R for Data Science](https://r4ds.had.co.nz). <a onclick="history.back()">↩︎</a>

### Tidy

The term "tidy" is part of REDCapTidieR's name because it underlies two key ideas of the package.

The first is the concept of [Tidy Data](https://vita.had.co.nz/papers/tidy-data.pdf). A rectangular data structure is tidy if:

1.  Each [variable](#variable) forms a [column](#column)
2.  Each observation forms a [row](#row)
3.  Each type of observational unit forms a table (i.e. the [granularity](#granularity) of rows in a table is consistent)

Data returned by the REDCap API (the "[block matrix](#block-matrix)") often satisfies the first two requirements of tidy data. However, if the [project](#project) contains both [repeating](#repeating-instrument) and [nonrepeating](#nonrepeating-instrument) instruments and/or events then the [granularity](#granularity) is inconsistent from row to row. A key function of the REDCapTidieR package is to break down the [block matrix](#block-matrix) by [instrument](#instrument). The resulting set of [data tibbles](#data-tibble) tends to be *tidier* than the block matrix, because the granularity within each individual data tibble is consistent. This makes it easy to work with them.

The second is the idea of [Tidy Tools](https://tidyverse.tidyverse.org/articles/manifesto.html), which is a set of design guidelines for the packages of the [Tidyverse](https://tidyverse.org/). Tidy tools should follow the following principles:

1.  Reuse existing data structures.
2.  Compose simple functions with the pipe.
3.  Embrace functional programming.
4.  Design for humans.

We strive to follow these principles in the design of the REDCapTidieR package. <a onclick="history.back()">↩︎</a>

### Variable {#variable}

A [column](#column) of a data frame or [tibble](#tibble). See also: [Column](#column). <a onclick="history.back()">↩︎</a>

### Variable label {#variable-label}

A human-readable description (label) attached to a [variable](#variable). See also: [labelled](#labelled). <a onclick="history.back()">↩︎</a>
