Add or remove variant implementations on a test or model function

These are developer-interface functions intended for package authors extending the statim framework with new method variants.

add_variant() is used as the left-hand side of the %<-% operator to register a variant() for a stat function and model type. "default" is frozen and cannot be added.

remove_variant() removes a previously registered "user"-originated variant. "package"-level entries are self-cleaning: they exist for the duration the registering package is loaded and vanish when it is unloaded.

Usage

add_variant(obj, model_type, name, origin = c("user", "package"))

remove_variant(obj, model_type, name)

Arguments

obj

A test or model function built with HTEST_FN() or MODEL_FN() (e.g. TTEST). Used to scope the registry key.

model_type

An S7 <var_id> class (e.g. x_by, S7::class_formula).

name

A string naming the variant to add.

origin

One of "user" (default, session-scoped) or "package" (load-scoped, intended for .onLoad()).

Value

An add_variant_call object, consumed by %<-%.

See also

stat_define(), variant(), agendas(), model_processor()

Examples

# Add a bootstrap variant for x_by (user level).
# .proc$x_data[[1]] is the response vector; .proc$group_data is the
# grouping data frame. See ?model_processor for all available keys.
add_variant(TTEST, x_by, "another_boot") %<-% variant(
    fn = function(.proc, .n = 1000L) {
        x = .proc$x_data[[1]]
        grp = as.character(.proc$group_data[[1]])
        lvls = unique(grp)
        x1 = x[grp == lvls[[1]]]
        x2 = x[grp == lvls[[2]]]
        boot_fn = function(d, i) mean(d[i, 1]) - mean(d[i, 2])
        b = boot::boot(data.frame(x1, x2), boot_fn, R = .n)
        boot::boot.ci(b, type = "perc")
    }
)

# Remove it, returning to the original slate
remove_variant(TTEST, x_by, "another_boot")

# Package level (inside .onLoad())
add_variant(TTEST, x_by, "another_boot", origin = "package") %<-% variant(
    fn = function(.proc, .n = 1000L) { ... }
)