library(term)
# term vectors are the labels used to reference values in
# vectors, matrices and arrays
term <- term(
  "alpha[1]", "alpha[2]", "beta[1,1]", "beta[2,1]",
  "beta[1,2]", "beta[2,2]", "sigma"
)
# they print like character vectors
term
#> <term[7]>
#> [1] alpha[1]  alpha[2]  beta[1,1] beta[2,1] beta[1,2] beta[2,2] sigma
# but are S3 class objects that also inherit from vctrs_vctr
class(term)
#> [1] "term"       "vctrs_vctr"

# consider a matrix of term values
set.seed(101)
estimate <- matrix(rnorm(4), nrow = 2)
estimate
#>            [,1]       [,2]
#> [1,] -0.3260365 -0.6749438
#> [2,]  0.5524619  0.2143595
# the term labels can be created using as_term()
term <- as_term(estimate, name = "b0")
term
#> <term[4]>
#> [1] b0[1,1] b0[2,1] b0[1,2] b0[2,2]
# and combined with the term values to create a coef table
library(tibble)
coef <- tibble(term = term, estimate = as.vector(estimate))
coef
#> # A tibble: 4 × 2
#>   term    estimate
#>   <term>     <dbl>
#> 1 b0[1,1]   -0.326
#> 2 b0[2,1]    0.552
#> 3 b0[1,2]   -0.675
#> 4 b0[2,2]    0.214

# the term vectors are readily sorted
coef[rev(order(coef$term)), ]
#> # A tibble: 4 × 2
#>   term    estimate
#>   <term>     <dbl>
#> 1 b0[2,2]    0.214
#> 2 b0[1,2]   -0.675
#> 3 b0[2,1]    0.552
#> 4 b0[1,1]   -0.326
# and the parameter names or parameter dimensions extracted
term <- term(
  "alpha[1]", "alpha[2]", "beta[1,1]", "beta[2,1]",
  "beta[1,2]", "beta[2,2]", "sigma"
)
pars(term)
#> [1] "alpha" "beta"  "sigma"
pdims(term)
#> $alpha
#> [1] 2
#> 
#> $beta
#> [1] 2 2
#> 
#> $sigma
#> [1] 1
# this can also be done for each term
pars_terms(term)
#> [1] "alpha" "alpha" "beta"  "beta"  "beta"  "beta"  "sigma"
tindex(term)
#> $`alpha[1]`
#> [1] 1
#> 
#> $`alpha[2]`
#> [1] 2
#> 
#> $`beta[1,1]`
#> [1] 1 1
#> 
#> $`beta[2,1]`
#> [1] 2 1
#> 
#> $`beta[1,2]`
#> [1] 1 2
#> 
#> $`beta[2,2]`
#> [1] 2 2
#> 
#> $sigma
#> [1] 1

# term vectors can be tested for whether they have (parseably) valid,
# (dimensionally) consistent and complete terms.
# valid terms
valid_term(term("a", "a[1]", "a [2]", " b [3  ] ", "c[1,10]"))
#> [1] TRUE TRUE TRUE TRUE TRUE
# invalid terms
valid_term(new_term(c("a a", "a[]", "a[2", " b[3 3]", "c[1,10]c")))
#> [1] FALSE FALSE FALSE FALSE FALSE
# consistent terms
consistent_term(term("a", "a[2]", "b[1,1]", "b[10,99]"))
#> [1] TRUE TRUE TRUE TRUE
# inconsistent terms
consistent_term(term("a", "a[2,1]", "b[1,1]", "b[10,99,1]"))
#> [1] FALSE FALSE FALSE FALSE
# complete terms
is_incomplete_terms(term("a", "a[2]", "b[1,1]", "b[2,1]"))
#> [1] FALSE
# incomplete terms
is_incomplete_terms(term("a", "a[3]", "b[1,1]", "b[2,2]"))
#> [1] TRUE

# term vectors can be checked using functions styled on those in the chk package
x <- term("a[1]", "a[3]")
vld_term(x, validate = "valid")
#> [1] TRUE
chk_term(x, validate = "complete")
#> Error:
#> ! All elements of term vector `x` must be complete.

term <- new_term(c("b[4]", "b   [2]", "b", "b[1", "b[2, 2]", "b", "a [ 1 ] ", NA))
term
#> <term[8]>
#> [1] b[4]       `b   [2]`  b          b[1        `b[2, 2]`  b          `a [ 1 ] `
#> [8] <NA>
# valid terms can be repaired (invalid terms are converted to missing values)
term <- repair_terms(term)
term
#> <term[8]>
#> [1] b[4]   b[2]   b[1]   <NA>   b[2,2] b[1]   a      <NA>
# the `term()` constructor rejects invalid terms
term("b[4]", "b   [2]", "b", "b[1", "b[2, 2]", "b", "a [ 1 ] ", NA)
#> Error in `term_impl()`:
#> ! All elements of term vector `string_args_term` must be valid.
# missing values can easily removed
term <- term[!is.na(term)]
term
#> <term[6]>
#> [1] b[4]   b[2]   b[1]   b[2,2] b[1]   a
# and only unique values retained
term <- unique(term)
term
#> <term[5]>
#> [1] b[4]   b[2]   b[1]   b[2,2] a
# a term vector can be sorted by parameter name and index
term <- sort(term)
term
#> <term[5]>
#> [1] a      b[1]   b[2]   b[4]   b[2,2]
# an inconsistent term removed
term <- term[term != "b[2,2]"]
term
#> <term[4]>
#> [1] a    b[1] b[2] b[4]
# and incomplete terms completed
term <- sort(complete_terms(term))
term
#> <term[5]>
#> [1] a    b[1] b[2] b[3] b[4]

install.packages("term")

install.packages("term", repos = c("https://poissonconsulting.r-universe.dev", "https://cloud.r-project.org"))

# install.packages("remotes")
remotes::install_github("poissonconsulting/term")