Parse Formula Variables

The parseFormula() function analyzes a given formula to identify and extract variables that match specified patterns. It is particularly useful for isolating variables enclosed within certain functions or constructs in the formula, such as asym(), det(), or any user-defined patterns.

Usage

parse_formula_vars(formula)

Arguments

formula

The initial formula for the model, typically specified using R's formula syntax (e.g., y ~ x + f(x1 + x2)).

Value

A list containing:

• response: The response variable(s) extracted from the formula.

• intercept: A logical value indicating whether the formula includes an intercept (default is TRUE).

• dot: A logical value indicating whether the formula includes a dot (.) representing all other variables (default is FALSE).

• outside: A vector of variables that are outside any specified patterns. It includes the variables that are not detected within the specified patterns in the formula.

• inside: A list where each element corresponds to a detected pattern (e.g., function name) and contains the variables found inside that pattern. For example, if the formula includes asym(x1 + x2), the inside list will have an element named "asym" containing the variables "x1" and "x2". This allows for easy identification of variables that are part of specific constructs in the formula.

See also

formula and gregexpr

Examples

# Parse formulas containing various collection types like ()
formula_ <- y ~ x +det(s -gg- d) + asymS(d2 -rr+ s)-mm(y1+y2+y3)+asym(k1+k2+k3)+trend-huseyin
# Extract variables
parse_formula_vars(formula_)
#> $response
#> [1] "y"
#> 
#> $intercept
#> [1] TRUE
#> 
#> $dot
#> [1] FALSE
#> 
#> $outside
#> [1] "x"       "trend"   "huseyin"
#> 
#> $inside
#> $inside$det
#> [1] "s"  "gg" "d" 
#> 
#> $inside$asymS
#> [1] "d2" "rr" "s" 
#> 
#> $inside$mm
#> [1] "y1" "y2" "y3"
#> 
#> $inside$asym
#> [1] "k1" "k2" "k3"
#> 
#>