Add <epiparameter> diagram to design principles vignette

DESCRIPTION

@@ -39,18 +39,20 @@ Suggests:
     bookdown,
     DT,
     ggplot2,
+    RColorBrewer,
     jsonlite,
     knitr,
     rmarkdown,
     spelling,
     testthat (>= 3.0.0),
-    vdiffr (>= 1.0.7)
+    vdiffr (>= 1.0.7),
+    visNetwork
 VignetteBuilder: 
     knitr
 Config/Needs/check: mrc-ide/epireview
 Config/Needs/website: epiverse-trace/epiversetheme, mrc-ide/epireview
-Config/testthat/edition: 3
 Config/potools/style: explicit
+Config/testthat/edition: 3
 Encoding: UTF-8
 Language: en-GB
 LazyData: true

vignettes/design_principles.Rmd

@@ -30,6 +30,108 @@ The output of the `epiparameter()` constructor function is an `<epiparameter>` o
 
 Other functions return the simplest type possible, this may be an atomic vector (including single element vectors), or un-nested lists.
 
+## Package architecture
+
+Much of the {epiparameter} package is centred around the `<epiparameter>` class. Here is a diagram showing the class with it's S3 methods (the diagram below is interactive so can adjusted if labels are overlapping).
+
+```{r, echo=FALSE, fig.width=8, fig.height=5}
+# read NAMESPACE
+namespace <- base::parseNamespaceFile("epiparameter", .libPaths()[1L]) # nolint: undesirable_function_linter
+s3methods <- namespace$S3methods
+epiparameter_class_methods <-
+  s3methods[which(s3methods[, 2] == "epiparameter"), 1]
+
+# create network with all methods around the central node
+getters <- c("family()", "get_citation()", "get_parameters()")
+modifiers <- c("discretise()", "as.function()")
+distribution_functions <- c("cdf()", "density()", "generate()", "quantile()")
+utilities <- c("print()", "plot()", "mean()", "c()", "format()")
+checkers <- c("is_epiparameter()", "is_parameterised()", "is_truncated()")
+conversions <- c(
+  "convert_params_to_summary_stats()", "convert_summary_stats_to_params()"
+)
+coercion <- "as.data.frame()"
+
+# add one to each for the intermediate group nodes
+groups <- data.frame(
+  group = c(
+    rep("Getters", length(getters) + 1),
+    rep("Modifiers", length(modifiers) + 1),
+    rep("Distribution functions", length(distribution_functions) + 1),
+    rep("Utilities", length(utilities) + 1),
+    rep("Checkers", length(checkers) + 1),
+    rep("Conversions", length(conversions) + 1),
+    rep("Coercion", length(coercion) + 1)
+  ),
+  functions = c(
+    c("Getters", getters),
+    c("Modifiers", modifiers),
+    c("Distribution functions", distribution_functions),
+    c("Utilities", utilities),
+    c("Checkers", checkers),
+    c("Conversions", conversions),
+    c("Coercion", coercion)
+  )
+)
+
+nodes <- data.frame(
+  id = seq_len(nrow(groups) + 1),
+  group = c("<epiparameter>", groups$group),
+  label = c("<epiparameter>", groups$functions),
+  shape = "box",
+  stringsAsFactors = FALSE
+)
+
+from <- seq_len(nrow(groups))
+
+# plus one for the central node
+to <- 2:(nrow(groups) + 2)
+
+for (grp in unique(groups$group)) {
+  # plus one for central node
+  from[which(groups$group == grp) + 1] <- min(which(groups$group == grp)) + 1
+}
+
+# set intermediate nodes to connect to central node
+from[groups$group == groups$functions] <- 1
+
+edges <- data.frame(
+  from = from,
+  to = to,
+  color = "black",
+  stringsAsFactors = FALSE
+)
+
+colours <- RColorBrewer::brewer.pal(
+  n = length(unique(nodes$group)),
+  name = "Set3"
+)
+
+# functions from parseNamespaceFile() need parentheses to match formatting
+epiparameter_class_methods <- paste0(epiparameter_class_methods, "()")
+if (!all(epiparameter_class_methods %in% groups$functions)) {
+  message(
+    "This diagram is out of date, as new methods have been added to the ",
+    "package which are not included."
+  )
+}
+
+library(visNetwork)
+visNetwork(nodes, edges) |>
+  visNodes(font = list(size = 18)) |>
+  visGroups(groupname = "<epiparameter>", color = colours[1]) |>
+  visGroups(groupname = "Getters", color = colours[2]) |>
+  visGroups(groupname = "Modifiers", color = colours[3]) |>
+  visGroups(
+    groupname = "Distribution functions",
+    color = colours[4]
+  ) |>
+  visGroups(groupname = "Utilities", color = colours[5]) |>
+  visGroups(groupname = "Checkers", color = colours[6]) |>
+  visGroups(groupname = "Conversions", color = colours[7]) |>
+  visGroups(groupname = "Coercion", color = colours[8])
+```
+
 ## Design decisions
 
 * The `<epiparameter>` class is designed to be a core unit for working with epidemiological parameters. It is designed in parallel to other epidemiological data structures such as a the `<contactmatrix>` class from the [{contactmatrix} R package](https://socialcontactdata.github.io/contactmatrix/index.html). The design principles of the `<epiparameter>` class are aligned with the [`<contactmatrix>` design principles](https://socialcontactdata.github.io/contactmatrix/articles/design-principles.html). These include: