Helpers to Compare Models — digest_partable • semeqmodels

Helper functions that compute and use hash digests for models (parameter tables) to facilitate comparisons.

Usage

digest_partable(
  partable,
  cols = getOption("semeqmodels.digest_cols", default = c("lhs", "op", "rhs", "block",
    "group", "free", "ustart", "start")),
  digits = getOption("semeqmodels.digest_digits", default = 6),
  sort_rows = TRUE,
  sort_by = getOption("semeqmodels.digest_sort_by", default = c("lhs", "op", "rhs",
    "block", "group")),
  algo = getOption("semeqmodels.algo", default = "xxhash32"),
  ...
)

add_digest(partable, ..., overwrite = FALSE)

get_digest(partable, ...)

add_digest_partables(partables, ..., overwrite = FALSE)

get_digest_partables(partables, ...)

Arguments

partable: A lavaan parameter table. If it is a lavaan output, the parameter table will be retrieved by lavaan::parameterTable().
cols: The columns to be used to compute the hash value. Note that start and ustart will be rounded based on digits, free will be converted to 0s and 1s (any values greater than 0 will be converted to 0), and start and ustart will be set to NA for free parameters.
digits: The number of digits when rounding ustart and start by round().
sort_rows: Whether the parameter tables will be sorted by cols before computing the hash value.
sort_by: The columns used when sorting the rows, if sort_rows is TRUE.
algo: The algorithm used to by digest::digest(). Note that the default value is different from that of digest::digest()
...: For digest_partable(), these are optional arguments to be passed to digest::digest(). For add_digest(), get_digest(), add_digest_partables(), and get_digest_partables(), these are arguments to be passed to digest_partable().
overwrite: Logical. If TRUE, the stored hash value, if it exists, will be overwritten. If FALSE, the stored hash value, if it exists, will not be overwritten.
partables: A list of lavaan parameter tables.

Value

The function digest_partable() returns a character string, the output of digest::digest().

The function add_digest() returns the parameter table, with the hash value stored in the attribute "digest".

The function get_digest() returns the hash value of a parameter table.

The function add_digest_partables returns the list of parameter tables, with hash values stored.

The function get_digest_partables returns a character vector, the outputs of get_digest() for the parameter tables.

Details

The function digest_partable() uses digest::digest() to compute a hash value for a parameter, after sorting some essential columns (see the cols argument) If two lavaan parameter tables are identical on the values for these columns, they should have the same hash value and will be considered as identical.

Note that there may be cases in which two models cannot be correctly identified using this approach. Nevertheless, they should be sufficient for typical models used in this package.

The function add_digest() computes the hash value of a parameter table and adds it to the attribute "digest" of the table. If the attribute is already set, it will not overwrite it unless overwrite is set to TRUE.

The function get_digest() retrieves the stored hash value from a parameter table, if available. If not available, it will call digest_partable() to compute the hash value.

The function add_digest_partables calls add_digest() on a list of parameter tables.

The function get_digest_partables calls get_digest() on a list of parameter tables.

Examples


library(lavaan)

# Model 1

mod1 <-
"
fx =~ x1 + x2 + x3
fm =~ m1 + m2 + m3
fy =~ y1 + y2 + y3
fm ~ fx
fy ~ fm + fx
"
fit1 <- sem(
          model = mod1,
          data = data_test_3_factor_3_item,
          do.fit = FALSE
        )

mod2 <-
"
fy =~ y1 + y2 + y3
fx =~ x1 + x2 + x3
fm =~ m1 + m2 + m3
fy ~ fm + fx
fm ~ fx
"
fit2 <- sem(
          model = mod2,
          data = data_test_3_factor_3_item,
          do.fit = FALSE
        )

pt1 <- parameterTable(fit1)
pt2 <- parameterTable(fit2)

pt1
#>    id lhs op rhs user block group free ustart exo label plabel start   est
#> 1   1  fx =~  x1    1     1     1    0      1   0         .p1. 1.000 1.000
#> 2   2  fx =~  x2    1     1     1    1     NA   0         .p2. 1.127 1.127
#> 3   3  fx =~  x3    1     1     1    2     NA   0         .p3. 0.756 0.756
#> 4   4  fm =~  m1    1     1     1    0      1   0         .p4. 1.000 1.000
#> 5   5  fm =~  m2    1     1     1    3     NA   0         .p5. 0.658 0.658
#> 6   6  fm =~  m3    1     1     1    4     NA   0         .p6. 0.669 0.669
#> 7   7  fy =~  y1    1     1     1    0      1   0         .p7. 1.000 1.000
#> 8   8  fy =~  y2    1     1     1    5     NA   0         .p8. 0.486 0.486
#> 9   9  fy =~  y3    1     1     1    6     NA   0         .p9. 0.502 0.502
#> 10 10  fm  ~  fx    1     1     1    7     NA   0        .p10. 0.000 0.000
#> 11 11  fy  ~  fm    1     1     1    8     NA   0        .p11. 0.000 0.000
#> 12 12  fy  ~  fx    1     1     1    9     NA   0        .p12. 0.000 0.000
#> 13 13  x1 ~~  x1    0     1     1   10     NA   0        .p13. 0.946 0.946
#> 14 14  x2 ~~  x2    0     1     1   11     NA   0        .p14. 0.751 0.751
#> 15 15  x3 ~~  x3    0     1     1   12     NA   0        .p15. 0.778 0.778
#> 16 16  m1 ~~  m1    0     1     1   13     NA   0        .p16. 0.874 0.874
#> 17 17  m2 ~~  m2    0     1     1   14     NA   0        .p17. 0.746 0.746
#> 18 18  m3 ~~  m3    0     1     1   15     NA   0        .p18. 0.597 0.597
#> 19 19  y1 ~~  y1    0     1     1   16     NA   0        .p19. 1.000 1.000
#> 20 20  y2 ~~  y2    0     1     1   17     NA   0        .p20. 0.702 0.702
#> 21 21  y3 ~~  y3    0     1     1   18     NA   0        .p21. 0.695 0.695
#> 22 22  fx ~~  fx    0     1     1   19     NA   0        .p22. 0.050 0.050
#> 23 23  fm ~~  fm    0     1     1   20     NA   0        .p23. 0.050 0.050
#> 24 24  fy ~~  fy    0     1     1   21     NA   0        .p24. 0.050 0.050
pt2
#>    id lhs op rhs user block group free ustart exo label plabel start   est
#> 1   1  fy =~  y1    1     1     1    0      1   0         .p1. 1.000 1.000
#> 2   2  fy =~  y2    1     1     1    1     NA   0         .p2. 0.486 0.486
#> 3   3  fy =~  y3    1     1     1    2     NA   0         .p3. 0.502 0.502
#> 4   4  fx =~  x1    1     1     1    0      1   0         .p4. 1.000 1.000
#> 5   5  fx =~  x2    1     1     1    3     NA   0         .p5. 1.127 1.127
#> 6   6  fx =~  x3    1     1     1    4     NA   0         .p6. 0.756 0.756
#> 7   7  fm =~  m1    1     1     1    0      1   0         .p7. 1.000 1.000
#> 8   8  fm =~  m2    1     1     1    5     NA   0         .p8. 0.658 0.658
#> 9   9  fm =~  m3    1     1     1    6     NA   0         .p9. 0.669 0.669
#> 10 10  fy  ~  fm    1     1     1    7     NA   0        .p10. 0.000 0.000
#> 11 11  fy  ~  fx    1     1     1    8     NA   0        .p11. 0.000 0.000
#> 12 12  fm  ~  fx    1     1     1    9     NA   0        .p12. 0.000 0.000
#> 13 13  y1 ~~  y1    0     1     1   10     NA   0        .p13. 1.000 1.000
#> 14 14  y2 ~~  y2    0     1     1   11     NA   0        .p14. 0.702 0.702
#> 15 15  y3 ~~  y3    0     1     1   12     NA   0        .p15. 0.695 0.695
#> 16 16  x1 ~~  x1    0     1     1   13     NA   0        .p16. 0.946 0.946
#> 17 17  x2 ~~  x2    0     1     1   14     NA   0        .p17. 0.751 0.751
#> 18 18  x3 ~~  x3    0     1     1   15     NA   0        .p18. 0.778 0.778
#> 19 19  m1 ~~  m1    0     1     1   16     NA   0        .p19. 0.874 0.874
#> 20 20  m2 ~~  m2    0     1     1   17     NA   0        .p20. 0.746 0.746
#> 21 21  m3 ~~  m3    0     1     1   18     NA   0        .p21. 0.597 0.597
#> 22 22  fy ~~  fy    0     1     1   19     NA   0        .p22. 0.050 0.050
#> 23 23  fx ~~  fx    0     1     1   20     NA   0        .p23. 0.050 0.050
#> 24 24  fm ~~  fm    0     1     1   21     NA   0        .p24. 0.050 0.050

digest_partable(pt1)
#> [1] "fd631766"
digest_partable(pt2)
#> [1] "fd631766"