Develop, adapt and maintain computational health economic models

• 1: Template module
• 2: Provide end users with a simple and consistent syntax for using model modules
• 3: Author and share model modules
• 3.1: Authoring model data structures
• 3.2: Authoring model algorithms
• 3.3: Dissemating citable, documented and quality assured model module libraries
• 4: Partially automate maintenance of a modelling project's website

1 - Template module

library(ready4) 

Motivation

A potentially attractive approach to modelling complex health systems is to begin with a relatively simple computational model and to progressively extend its scope and sophistication. Such an approach could be described as “modular” if it is possible to readily combine multiple discrete modelling projects (potentially developed by different modelling teams) that each independently describe distinct aspects of the system being modelled.

Implementation

The ready4 facilitates modular model development by supplying a template module that enables model developers to avail of the encapsulation and inheritance features of Object Oriented Programming (OOP). The ready4 framework uses two of R’s systems for implementing OOP - S3 and S4. An in-depth explanation of R’s different class system is beyond the scope of this article, but is explored in Hadley Wickham’s Advanced R handbook. However, it is useful to know some very high level information about S3 and S4 classes:

• S4 classes are frequently said to be “formal”, “strict” or “rigorous”. The elements of an S4 class are called slots and the type of data that each slot is allowed to contain is specified in the class definition. An S4 class can be comprised of slots that contain different types of data (e.g. a slot that contains a character vector and another slot that contains tabular data).

• S3 classes are often described as “simple”, “informal” and “flexible”. S3 objects attach an attribute label to base type objects (e.g. a character vector, a data.frame, a list), which in turn is used to work out what methods should be applied to the class.

Use

ready4 Model Modules

As we use the term, a “model module” is comprised of both a data-structure (an S4 class) and the algorithms (or “methods”) that are associated with that data-structure. Model modules can be created from a template - the ready4 package’s Ready4Module class.

We can create an object (X) from the Ready4Module template using the following command.

X <- Ready4Module()

However, if we inspect X we can see it is of limited use as it contains no data other than an empty element called dissemination_1L_chr.

str(X)
#> Formal class 'Ready4Module' [package "ready4"] with 1 slot
#>   ..@ dissemination_1L_chr: chr NA

The Ready4Module class is therefore not intended to be called directly. Instead, the purpose of Ready4Module is to be the parent class of other model modules. Prototype tools for authoring modules from this template are described here.

ready4 Model Sub-modules

In ready4, S3 classes are principally used to help define the structural properties of slots (elements) of model modules and the methods that can be applied to these slots. S3 classes created for these purposes are called sub-modules.

2 - Provide end users with a simple and consistent syntax for using model modules

library(ready4) 

Motivation

Transparency is one of the underpinning principles of ethical modelling practice. One way to improve the transparency of computational health economic models is to ensure that the programs implementing model analyses can be meaningfully inspected by readers with different levels of technical expertise. Even non-technical readers should be able to follow the high-level logic implemented by model algorithms. If multiple analysis programs are written using a common simplified syntax then reviewers of those programs need to contend with relatively fewer new concepts.

Implementation

ready4 provides a simple syntax that can be consistently applied to attach algorithms (methods) to model modules. It does so by taking advantage of the abstraction and polymorphism features of Object Oriented Programing and R’s use of generic functions. Generic functions don’t implement algorithms themselves - their most salient features are a name and a high level description of the type of task that any method associated with that generic should perform. Whenever a developer creates a method for classes that use R’s S4 and S3 systems (the types used for model modules and sub-modules), they can associate that method with a generic that has a description that is a good match for the algorithm being implemented.

Use

ready4 includes a number of core generic functions which describe the main types of method to be implemented by model modules. These generics correspond exactly to the “core”, “slot” and “extended” commands described in another article.

Notably, the ready4 package does not associate any core or extended methods with the Ready4Module template module. Instead, model developers need to decide which core and extended generics they associate with the modules they derive from the Ready4Module template. This decision is typically made when authoring the methods associated with model modules.

Currently, the only methods defined for Ready4Module are slot-methods. By default, these slot methods are inherited by all modules derived from the Ready4Module template. These methods can be itemised using the get_methods function.

get_methods()
#>  [1] "authorSlot"        "characterizeSlot"  "depictSlot"        "enhanceSlot"       "exhibitSlot"       "ingestSlot"        "investigateSlot"   "manufactureSlot"  
#>  [9] "metamorphoseSlot"  "procureSlot"       "prognosticateSlot" "ratifySlot"        "reckonSlot"        "renewSlot"         "shareSlot"

3 - Author and share model modules

3.1 - Authoring model data structures

library(ready4class)
library(ready4show)
library(ready4use)

Motivation

The ready4 framework uses object oriented programming (OOP) to implement modular approaches to computational models of mental health systems. That means that a standardised approach to developing modules (S4 classes) and sub-modules (S3 classes) is required. ready4class provides the tools to implement this workflow.

Workflow

Prototyes, constructor and manifest

The main classes exported as part of ready4class are readyclass_manifest and ready4class_constructor. ready4class_pt_lup is a tibble based ready4 sub-module, which contains metadata on the prototypes of classes that can be used as sub-components of ready4 modules and sub-modules (for example a tibble based class can be used as a slot in an S4 class). When authoring ready4 R packages, you will create a ready4class_pt_lup instance and store it in an online repository that you have write permissions to. As you create new ready4 modules and sub-modules using ready4class tools, your ready4class_pt_lup object will be updated so that these classes can be made available to any future modules or sub-modules that you author. The ready4class_pt_lup sub-module recently used in workflows for authoring ready4 modules is reproduced below.

x <- ready4use::Ready4useRepos(gh_repo_1L_chr = "ready4-dev/ready4",
                               gh_tag_1L_chr = "Documentation_0.0") %>%
  ingest(fls_to_ingest_chr = "prototype_lup",
         metadata_1L_lgl = F) 
x %>%
  exhibit(scroll_box_args_ls = list(width = "100%"))

ready4class_constructor is another tibble based ready4 sub-module that summarises the desired features of the ready4 modules and sub-modules that you are authoring. An instance of ready4class_constructor is combined with a ready4fun_manifest sub-module to create a ready4class_manifest sub-module. Instances of ready4class_constructor are most efficiently created using the make_pt_ready4class_constructor function.

y <- make_pt_ready4class_manifest(ready4fun::ready4fun_manifest(),
                                  constructor_r3 = ready4class_constructor()) %>%
  ready4class_manifest()

Typical use

The most important method included in ready4class is the author method for the ready4class_manifest sub-module, that enhances the author method defined for the ready4fun_manifest so that consistently documented R package classes are also generated.

## Not run
author(y)

Examples

ready4class sub-modules and methods are not intended for independent use, but instead should be deployed as part of ready4pack R package authoring workflow.

Future documentation

It should be noted that some ready4class methods require files of a standardised format to be saved in specific sub-directories of the package data-raw directory. Detailed instructions on how to prepare these files are not yet available, but will be outlined in documentation to be released in 2022.

3.2 - Authoring model algorithms

library(ready4)
library(ready4fun)

Motivation

The ready4 framework uses an object-oriented programming (OOP) approach to implement computational health economic models. One motivation for using OOP is the concept of “abstraction” - making things as simple as possible for end-users of ready4 modules by exposing the minimal amount of code required to implement each method.

However, some users of the ready4 modules will want to “look under the hood” and examine the code that implements module algorithms in much more detail. Reasons to do so include to:

• gain detailed insight into how methods are implemented;
• test individual sub-components of methods as part of code verification and model validation checks;
• re-use sub-components of existing methods when authoring new methods.

To help facilitate achieving these objectives, methods associated with ready4 modules can be de-composed into functions that can be used independent of ready4 modules. However, these functions need to be documented and will be easier to comprehend if they adopt a consistent house style (e.g. naming conventions). ready4fun provides workflow tools (classes, methods, functions and datasets) to achieve these goals.

ready4fun function authoring taxonomies, abbreviations and workflow

The ready4fun package uses taxonomy and abbreviation datasets to ensure standardised function code style and documentation.

Function names begin with a meaningful verb

Consistent with a naming convention popular in the R development community, all functions authored with the ready4 framework need to begin with a verb. Furthermore, the choice of verb is meaningful - it communicates something about the type of task a function implements. For example, all functions beginning with the word “fit” will fit a model of a specified type to a dataset. The definitions of all meaningful verbs used in functions authored for a ready4 framework model implementation can be retrieved using get_fn_types(), which by default returns a dataset instance of the ready4fun_functions submodule.

x <- get_fn_types(gh_repo_1L_chr = "ready4-dev/ready4")
class(x)
#> [1] "ready4fun_functions" "tbl_df"              "tbl"                 "data.frame"

exhibit(x,select_int = 1:2, scroll_box_args_ls = list(width = "100%"))

Function inputs and outputs have meaningful suffices

The type of input (arguments) required and output (return) produced by a function can be efficiently communicated by using meaningful suffices. For example all objects ending in “_chr” are character vectors and all objects ending in “_int” are integer vectors. Definitions of all meaningful suffices used in functions authored for a ready4 framework model implementation can be retrieved using get_obj_types(), which by default returns a dataset instance of the ready4fun_objects submodule.

y <- get_obj_types(gh_repo_1L_chr = "ready4-dev/ready4")
class(y)
#> [1] "ready4fun_objects" "tbl_df"            "tbl"               "data.frame"

exhibit(y, select_int = 1:2, scroll_box_args_ls = list(width = "100%"))

Consistent use of abbreviations

Further information about the purpose of a function and the nature of its inputs and outputs can be encoded by using naming conventions that make consistent use of abbreviations. A master table of the abbreviations used in a ready4 framework model implementation can be retrieved using get_abbrs(), which by default returns a dataset instance of the ready4fun_abbreviations submodule.

z <- get_abbrs(gh_repo_1L_chr = "ready4-dev/ready4")
class(z)
#> [1] "ready4fun_abbreviations" "tbl_df"                  "tbl"                     "data.frame"

exhibit(z %>% head(50), select_int = 1:2, scroll_box_args_ls = list(width = "100%"))

The ready4fun_abbreviations submodule is searchable. It is therefore possible to see if an abbreviation has been defined for an existing word or phrase…

procure(z,"template")
#> # A tibble: 2 × 3
#>   short_name_chr long_name_chr plural_lgl
#>   <chr>          <chr>         <lgl>     
#> 1 tmpl           template      FALSE     
#> 2 tmpls          templates     TRUE

…and to look-up the meaning of an abbreviation…

procure(z,"org",type_1L_chr = "extension")
#> # A tibble: 2 × 3
#>   short_name_chr long_name_chr plural_lgl
#>   <chr>          <chr>         <lgl>     
#> 1 org            organisation  FALSE     
#> 2 orgs           organisations TRUE

…or whether a potential abbreviation has already been defined.

procure(z,"org", type_1L_chr = "extension", what_1L_chr = "string")
#> [1] "org"  "orgs"

Workflow

Manifest

The main class exported as part of ready4fun is the ready4 sub-module ready4fun_manifest which is used to specify metadata (including details of the repository in which the fn_types_lup, seed_obj_lup_tb and abbreviations_lup objects are stored) for the functions being authored and the R package that will contain them.

x <- ready4fun_manifest()

Typical Usage

A ready4fun_manifest object is most efficiently created with the aid of the make_pkg_desc_ls and make_manifest functions rather than a direct call to the ready4fun_manifest() function.

## Not run
x <- ready4fun::make_pkg_desc_ls(
  pkg_title_1L_chr = "Your Package Title",
  pkg_desc_1L_chr = "Your Package Description.",
  authors_prsn = c(
    utils::person("Author 1 Name",
      role = c("aut", "cre")
    ),
    utils::person("Author 2 Name", role = c("cph"))
  ),
  urls_chr = c(
    "Package website url",
    "Package source code url",
    "Project website"
  )
) %>%
  ready4fun::make_manifest(
    copyright_holders_chr = "Organisation name",
    custom_dmt_ls = ready4fun::make_custom_dmt_ls(user_manual_fns_chr = c("Functions to be included in main user manual are itemised here")),
    dev_pkgs_chr = c("Any development package dependencies go here"),
    path_to_pkg_logo_1L_chr = "Local path to package logo goes here",
    piggyback_to_1L_chr = "GitHub Release Repository to which supporting files will be uploaded",
    ready4_type_1L_chr = "authoring",
    zenodo_badge_1L_chr = "DOI badge details go here"
  )

The main method defined for ready4fun_manifest is author which, assuming the raw undocumented function files are saved in the appropriate directories, will author an R package in which all functions are consistently documented.

## Not run
author(x)

Examples

The ready4fun_manifest sub-module and its methods along with the make_pkg_desc_ls and make_manifestfunctions are designed to be used as part of the ready4pack R package authoring workflow. That vignette includes links to two examples of where the ready4pack workflow has been used to author R package. To illustrate how readyfun tools used as part of that workflow are used to document functions, we are just going to focus on the program used to create the ready4show package.

That program makes use of ready4fun tools that read all undocumented package functions, performs automated checks to ensure that these functions appropriately use the taxonomies and abbreviations mentioned previously (prompting authors to make specific amendments if they do not) and then rewrites these functions to the package R directory, appending tags (with the aid of the sinew package) that will generate meaningful documentation.

For example, one of the functions to be documented is the knit_from_tmpl, which is transformed to a version with tags. The tags added to all functions are then used to generate the package documentation, including the package manual. Two versions of the ready4show package manual are generated - a slimmed down version for end-users and a more detailed inventory of contents intended for developers.

Future documentation

Detailed guidance for how to apply ready4fun workflow tools has yet to be prepared but is planned for 2024.

3.3 - Dissemating citable, documented and quality assured model module libraries

library(ready4)
library(ready4fun)
library(ready4class)
library(ready4pack)

ready4pack is a toolkit for bundling collections of modules for computational health economic models authored with the ready4 framework as R packages that are:

• Citable (with a Zenodo generated DOI and an algorithm generated CITATION file);
• Community-minded (applying deprecation conventions supported by lifecycle);
• Documented (applying a function self-documenting algorithm that extends sinew, deploying a GitHub pages hosted and pkgdown generated website and authoring PDF manuals stored in a GitHub Release via piggyback);
• Internally consistent implementing automated checks to ensure consistency in naming conventions, etc;
• Licensed (via a usethis generated GPL-3 license);
• Quality assured (using continuous integration via GitHub actions and R-CMD-Check); and
• Versioned (applying usethis version increments).

ready4pack extends ready4 framework tools for authoring module algorithms (ready4fun) and data structures (ready4class) and wraps functions from a number of third party R development workflow tools (such as devtools). ready4pack integrates these tools in a common workflow, while adding tools for authoring and documenting datasets to be shipped with model module R packages.

A combination of the ready4_pack_manifest class and author method are used to implement this workflow. This workflow has been used to author all public versions of the ready4 R packages available in the ready4 github repository.

Workflow

Manifest

The main class exported as part of ready4pack is readypack_manifest list based ready4 sub-module, that extends the ready4fun_manifest and ready4class_manifest sub-modules.

Typical usage

readypack_manifest sub-module is most efficiently created with the aid of the make_pt_ready4pack_manifest function and combines instances of the ready4fun_manifest and ready4class_constructor sub-modules.

x <- make_pt_ready4pack_manifest(ready4fun::ready4fun_manifest(),
                                 constructor_r3 = ready4class::ready4class_constructor()) %>%
  ready4pack_manifest()

The main method defined for readypack_manifest is author which extends the author method for ready4class_manifest to author a consistently documented R package.

## Not run
author(x)

Examples

Workflow example one

The program to author and document the ready4show package is relatively simple and authors:

• the ready4show package CITATION, DESCRIPTION, LICENSE and README files;

• all files in the ready4show package R directory;

• the ready4show package website;

• two versions of the ready4show package manual - a slimmed down version for end-users and a more detailed inventory of contents intended for developers;

• an initial ready4show release for hosting supporting files, the creation of which will trigger archiving on Zenodo with a ready4show package DOI; and

• an R-CMD-check continuous integration algorithm to be implemented each time a new version of ready4show is pushed to the main branch of the GitHub source code repository.

Workflow example two

The program to author and document the youthvars package is a bit more complex as it includes syntax to create package datasets. In addition to the package datasets, the algorithm creates content corresponding to the previous example, specifically:

• the youthvars package CITATION, DESCRIPTION, LICENSE and README files;

• all files in the youthvars package R directory;

• the youthvars package website;

• two versions of the youthvars package manual - a slimmed down version for end-users and a more detailed inventory of contents intended for developers;

• an initial youthvars release for hosting supporting files, the creation of which will trigger archiving on Zenodo with a youthvars package DOI; and

• an R-CMD-check continuous integration algorithm to be implemented each time a new version of youthvars is pushed to the main branch of the GitHub source code repository.

Future documentation

A more detailed guide to using ready4pack will be created in 2023.

4 - Partially automate maintenance of a modelling project's website

library(ready4) 

Motivation

Manually keeping track of modules libraries, programs, reporting templates and datasets authored by different teams and stored in different locations can be an onerous undertaking. The ready4 library therefore includes tools to allow a modelling project’s maintainers to perform automated searches for model artefacts and to output tabular summaries of these assets in formats suitable for inclusion on a project documentation website.

Implementation

The ready4 library includes tools to allow a modelling project’s maintainers to partially automate searching for and creating summaries of relevant modelling project assets (e.g. tutorials, releases, etc.) that are suitable for inclusion on documentation website pages.

Use

The documentation website maintenance tools in the ready4 library are designed to be used on a docsy documentation website derived from this template repository. An example of a website created from this template is the readyforwhatsnext model project website, for which source code is available here.

The write_to_render_post is the main ready4 function used specifically for website maintenance tasks. Importantly, the non-CRAN library hugodown needs to be installed to use this function.

write_to_render_post is designed for help overcome practical challenges of rendering RMD or Rmarkdown files (pareticularly those sourced from an individual module library’s documentation website) to Markdown output in an overall modelling project website. Examples of its use are in this script that is run when updating the readyforwhatsnext project website. The RMD / Rmarkdown files rendered by this example script call other useful functions from the ready4 package, such as:

• get_libraries_tb, update_libraries_tb and print_packages for updating details on module libraries (see this example)

• make_modules_tb and print_modules for updating details on individual modules (see this example)

• make_datasets_tb and print_data for updating details on module datasets (see this example)

• get_datasets_tb, make_dss_tb and make_ds_releases_tbl for updating release statuses of module datasets (see this RMD file and its output)

• make_programs_tbl for updating details on analysis programs or reporting sub-routines that use model modules (see this RMD file and its associated output as well as this RMD file and its output)

• make_code_releases_tbl for updating release statuses of module libraries and programs or reporting sub-routines that use model modules (see this RMD file and its output)