Rollups of summaries of variables with indices, version 2

[mjskay]

Summary

Now that some improved index-handling code is in, I thought I'd take a second attempt at rollups of summaries of variables with indices. This is a PR that will close #43 if it goes forward.

This is based on @jsocolar's #152, except I have iterated on the interface somewhat to be a bit more generic. It allows arbitrary rollup functions to be given on a per-original-summary-column basis, and supplies both overall default rollup functions and summary-specific rollup functions (e.g. having the ess functions rollup with min and rhat functions with max by default).

Demo:

x <- example_draws()

# you can roll up summaries of array-like variables by rolling up draws
# objects directly; this will apply the default options of summarise_draws()
rollup_summary(x)
#> <rollup_summary>:
#> 
#> $unrolled (variables that have not been rolled up): 
#> # A tibble: 2 × 10
#>   variable  mean median    sd   mad     q5   q95  rhat ess_bulk ess_tail
#>   <chr>    <dbl>  <dbl> <dbl> <dbl>  <dbl> <dbl> <dbl>    <dbl>    <dbl>
#> 1 mu        4.18   4.16  3.40  3.57 -0.854  9.39  1.02     558.     322.
#> 2 tau       4.16   3.07  3.58  2.89  0.309 11.0   1.01     246.     202.
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 1 × 17
#>   variable dim   mean_min mean_max median_min median_max sd_min sd_max mad_min
#>   <chr>    <chr>    <dbl>    <dbl>      <dbl>      <dbl>  <dbl>  <dbl>   <dbl>
#> 1 theta    8         3.04     6.75       3.72       5.97   4.63   6.80    4.25
#> # ℹ 8 more variables: mad_max <dbl>, q5_min <dbl>, q5_max <dbl>, q95_min <dbl>,
#> #   q95_max <dbl>, rhat_max <dbl>, ess_bulk_min <dbl>, ess_tail_min <dbl>

# or summarise draws objects first to pick the desired summary measures
# (note that ess_bulk is only rolled up using min by default)
ds <- summarise_draws(x, "mean", "sd", "ess_bulk")
rollup_summary(ds)
#> <rollup_summary>:
#> 
#> $unrolled (variables that have not been rolled up): 
#> # A tibble: 2 × 4
#>   variable  mean    sd ess_bulk
#>   <chr>    <dbl> <dbl>    <dbl>
#> 1 mu        4.18  3.40     558.
#> 2 tau       4.16  3.58     246.
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 1 × 7
#>   variable dim   mean_min mean_max sd_min sd_max ess_bulk_min
#>   <chr>    <chr>    <dbl>    <dbl>  <dbl>  <dbl>        <dbl>
#> 1 theta    8         3.04     6.75   4.63   6.80         312.

# rollups work on variables of any dimension
x <- example_draws(example = "multi_normal")
rollup_summary(x)
#> <rollup_summary>:
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 2 × 17
#>   variable dim   mean_min mean_max median_min median_max sd_min sd_max mad_min
#>   <chr>    <chr>    <dbl>    <dbl>      <dbl>      <dbl>  <dbl>  <dbl>   <dbl>
#> 1 mu       3       0.0514    0.186     0.0575      0.184  0.112  0.314   0.131
#> 2 Sigma    3,3    -2.10      8.12     -2.11        8.02   0.165  0.946   0.173
#> # ℹ 8 more variables: mad_max <dbl>, q5_min <dbl>, q5_max <dbl>, q95_min <dbl>,
#> #   q95_max <dbl>, rhat_max <dbl>, ess_bulk_min <dbl>, ess_tail_min <dbl>

# you can roll up only some variables
rollup_summary(x, variable = "Sigma")
#> <rollup_summary>:
#> 
#> $unrolled (variables that have not been rolled up): 
#> # A tibble: 3 × 10
#>   variable   mean median    sd   mad     q5   q95  rhat ess_bulk ess_tail
#>   <chr>     <dbl>  <dbl> <dbl> <dbl>  <dbl> <dbl> <dbl>    <dbl>    <dbl>
#> 1 mu[1]    0.0514 0.0575 0.112 0.131 -0.130 0.225  1.01     677.     356.
#> 2 mu[2]    0.111  0.104  0.199 0.198 -0.208 0.449  1.00     566.     426.
#> 3 mu[3]    0.186  0.184  0.314 0.315 -0.322 0.715  1.02     650.     334.
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 1 × 17
#>   variable dim   mean_min mean_max median_min median_max sd_min sd_max mad_min
#>   <chr>    <chr>    <dbl>    <dbl>      <dbl>      <dbl>  <dbl>  <dbl>   <dbl>
#> 1 Sigma    3,3      -2.10     8.12      -2.11       8.02  0.165  0.946   0.173
#> # ℹ 8 more variables: mad_max <dbl>, q5_min <dbl>, q5_max <dbl>, q95_min <dbl>,
#> #   q95_max <dbl>, rhat_max <dbl>, ess_bulk_min <dbl>, ess_tail_min <dbl>

# you can specify the rollup functions to apply to all summaries by passing
# unnamed parameters ...
rollup_summary(x, "mean", "min")
#> <rollup_summary>:
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 2 × 17
#>   variable dim   mean_mean mean_min median_mean median_min sd_mean sd_min
#>   <chr>    <chr>     <dbl>    <dbl>       <dbl>      <dbl>   <dbl>  <dbl>
#> 1 mu       3         0.116   0.0514       0.115     0.0575   0.208  0.112
#> 2 Sigma    3,3       1.01   -2.10         0.989    -2.11     0.387  0.165
#> # ℹ 9 more variables: mad_mean <dbl>, mad_min <dbl>, q5_mean <dbl>,
#> #   q5_min <dbl>, q95_mean <dbl>, q95_min <dbl>, rhat_max <dbl>,
#> #   ess_bulk_min <dbl>, ess_tail_min <dbl>

# ... or use names to specify rollup functions for specific summaries
rollup_summary(x, mean = "sd", median = "min")
#> <rollup_summary>:
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 2 × 15
#>   variable dim   mean_sd median_min sd_min sd_max mad_min mad_max q5_min q5_max
#>   <chr>    <chr>   <dbl>      <dbl>  <dbl>  <dbl>   <dbl>   <dbl>  <dbl>  <dbl>
#> 1 mu       3      0.0673     0.0575  0.112  0.314   0.131   0.315 -0.322 -0.130
#> 2 Sigma    3,3    3.19      -2.11    0.165  0.946   0.173   0.941 -2.87   6.71 
#> # ℹ 5 more variables: q95_min <dbl>, q95_max <dbl>, rhat_max <dbl>,
#> #   ess_bulk_min <dbl>, ess_tail_min <dbl>

# this unnamed for default / named for specific approach is also used to
# specify the default rollups in the `.funs` parameter. Its default value is:
default_rollups()
#> [[1]]
#> [1] "min" "max"
#> 
#> $ess_basic
#> [1] "min"
#> 
#> $ess_bulk
#> [1] "min"
#> 
#> $ess_mean
#> [1] "min"
#> 
#> $ess_median
#> [1] "min"
#> 
#> $ess_quantile
#> [1] "min"
#> 
#> $ess_sd
#> [1] "min"
#> 
#> $ess_tail
#> [1] "min"
#> 
#> $rhat
#> [1] "max"
#> 
#> $rhat_basic
#> [1] "max"
#> 
#> $rhat_nested
#> [1] "max"

# rollups can be chained to provide different rollup functions to
# different variables
x |>
 summarise_draws("mean", "sd") |>
 rollup_summary(variable = "mu", sd = "min") |>
 rollup_summary(variable = "Sigma", sd = "max")
#> <rollup_summary>:
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 2 × 6
#>   variable dim   mean_min mean_max sd_min sd_max
#>   <chr>    <chr>    <dbl>    <dbl>  <dbl>  <dbl>
#> 1 mu       3       0.0514    0.186  0.112 NA    
#> 2 Sigma    3,3    -2.10      8.12  NA      0.946

# you could ignore NAs on a specific rollup using an anonymous function, 
# though is is perhaps a bit cludgy 
x2 <- draws_rvars(x = c(rvar_rng(rnorm, 5), NA))
rollup_summary(x2, min)
#> <rollup_summary>:
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 1 × 11
#>   variable dim   mean_min median_min sd_min mad_min q5_min q95_min rhat_max
#>   <chr>    <chr>    <dbl>      <dbl>  <dbl>   <dbl>  <dbl>   <dbl>    <dbl>
#> 1 x        6           NA         NA     NA      NA     NA      NA       NA
#> # ℹ 2 more variables: ess_bulk_min <dbl>, ess_tail_min <dbl>
rollup_summary(x2, list(min = \(x) min(x, na.rm = TRUE)))
#> <rollup_summary>:
#> 
#> $rolled (variables that have been rolled up): 
#> # A tibble: 1 × 11
#>   variable dim   mean_min median_min sd_min mad_min q5_min q95_min rhat_max
#>   <chr>    <chr>    <dbl>      <dbl>  <dbl>   <dbl>  <dbl>   <dbl>    <dbl>
#> 1 x        6      -0.0320    -0.0405  0.985   0.985  -1.67    1.60       NA
#> # ℹ 2 more variables: ess_bulk_min <dbl>, ess_tail_min <dbl>

That last bit about NAs is IMO the weakest part of the API at the moment. Not sure if it needs fixing. One option is to add an overall na.rm = TRUE option to remove NAs before passing to the rollup functions. Could also allow NAs to be removed from specific summaries with a named argument; like na.rm = c(FALSE, ess_bulk = TRUE) or something like that.

Pinging folks who seemed interested in this from previous issues: @avehtari @paul-buerkner @jgabry @jsocolar @andrewgelman

Copyright and Licensing

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• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)