# Micro files

## Use case

`px_micro()` exists to support a specific use case for Statistics Greenland.

They use it to create small PX-files to showcase and present metadata from a lager data set which cannot be made publicly available. See an example on Statistic Greenland’s microdata for Research and Analysis.

## `px_micro()`

Apart from `px_save()`, `px_micro()` is the only other function that can save px objects as PX-files.

`px_micro()` turns a px object into many smaller PX-files, each containing a subset of the variables in the original px object.

## Input data

The basis of micro files are usually a data set which doesn’t have a count variable (like most PX-files). `px_micro()` will instead create a count of each individual variable.

In this example we will use the built-in data data set `greenlanders`.

    library(pxmake)

    greenlanders |>
      dplyr::sample_n(10) |>
      dplyr::arrange_all()
    #> # A tibble: 10 × 4
    #>    cohort gender   age municipality
    #>    <chr>  <chr>  <int> <chr>
    #>  1 A      female    21 Sermersooq
    #>  2 A      female    59 Qeqertalik
    #>  3 A      male      24 Kujalleq
    #>  4 A      male      48 Qeqqata
    #>  5 A      male      63 Avannaata
    #>  6 B      female    32 Kujalleq
    #>  7 B      female    73 Avannaata
    #>  8 B      male      44 Qeqertalik
    #>  9 B      male      62 Sermersooq
    #> 10 B      male      98 Qeqertalik

## How to create micro files

Create a px object with `px()`, and pass it to `px_micro()`.

    # Create px object
    x <- px(greenlanders)

    # Create folder for micro files
    micro_dir <- file.path("micro_files")
    dir.create(micro_dir)

    # Write micro files to folder
    px_micro(x, out_dir = micro_dir)

The folder now contains three PX-files, one for each variable except ‘age’.

    list.files(micro_dir)
    #> [1] "cohort.px"       "gender.px"       "municipality.px"

The reason ‘age’ didn’t get a PX-file is because it is the HEADING variable in `x`, and `px_micro()` creates a file for each non-HEADING variable. Instead the HEADNING variable is used in all the created PX-files.

    # Print HEADING variables
    px_heading(x)
    #> [1] "age"

    # Print non-HEADING variables
    c(px_stub(x), px_figures(x))
    #> [1] "cohort"       "gender"       "municipality"

In this case, we want ‘cohort’ to be heading, and to create a PX-file for ‘gender’, ‘age’ and ‘municipality’.

    x2 <-
      x |>
      px_stub("age") |> # Change age to STUB
      px_heading("cohort") # Change cohort to HEADING

    # Clear folder
    unlink(file.path(micro_dir, "*.px"))

    px_micro(x2, out_dir = micro_dir)

The folder now contains the files we wanted.

    list.files(micro_dir)
    #> [1] "age.px"          "gender.px"       "municipality.px"

Each file contains one of the three variables as STUB, ‘cohort’ as HEADING, and a variable ‘n’ which is the count of each combination of the variables.

    px(file.path(micro_dir, "age.px"))$data
    #> # A tibble: 120 × 3
    #>    age   cohort     n
    #>    <chr> <chr>  <dbl>
    #>  1 18    A         NA
    #>  2 18    B          1
    #>  3 19    A         NA
    #>  4 19    B          1
    #>  5 20    A         NA
    #>  6 20    B          1
    #>  7 21    A          3
    #>  8 21    B         NA
    #>  9 22    A          1
    #> 10 22    B         NA
    #> # ℹ 110 more rows

    px(file.path(micro_dir, "gender.px"))$data
    #> # A tibble: 4 × 3
    #>   gender cohort     n
    #>   <chr>  <chr>  <dbl>
    #> 1 female A         31
    #> 2 female B         18
    #> 3 male   A         23
    #> 4 male   B         28

    px(file.path(micro_dir, "municipality.px"))$data
    #> # A tibble: 10 × 3
    #>    municipality cohort     n
    #>    <chr>        <chr>  <dbl>
    #>  1 Avannaata    A         11
    #>  2 Avannaata    B         11
    #>  3 Kujalleq     A         12
    #>  4 Kujalleq     B          7
    #>  5 Qeqertalik   A         13
    #>  6 Qeqertalik   B          5
    #>  7 Qeqqata      A          9
    #>  8 Qeqqata      B         11
    #>  9 Sermersooq   A          9
    #> 10 Sermersooq   B         12

## Keyword values

In general the keyword values from the px object are carried over to the micro files. This is the case for keywords like ‘MATRIX’, ‘SUBJECT-CODE’, ‘CONTACT’, ‘LANGUAGE’, ‘CODEPAGE’, etc.

To change keywords across all the micro files, the easiest is to change them in the px object before calling `px_micro()`.

    # Change CONTACT in all micro files
    x2 |>
      px_contact("Johan Ejstrud") |>
      px_micro(out_dir = micro_dir)

However, some keywords need to be changed individually for each micro file. To do so, create a data frame with the column ‘variable’ and a column for each px keyword to change.

    individual_keywords <- tibble::tribble(
      ~variable, ~px_description,
      "age", "Age count 18-99",
      "gender", "Gender count",
      "municipality", "Municipality 2024"
    )

Supply this dataframe to the `keyword_values` argument of `px_micro()`.

    px_micro(x2, out_dir = micro_dir, keyword_values = individual_keywords)

DESCRIPTION is changed in the micro files:

    px(file.path(micro_dir, "age.px")) |> px_description()
    #> [1] "Age count 18-99"
    px(file.path(micro_dir, "gender.px")) |> px_description()
    #> [1] "Gender count"
    px(file.path(micro_dir, "municipality.px")) |> px_description()
    #> [1] "Municipality 2024"

### Multilingual files

For multilingual files add a ‘language’ column to `keyword_values`.

    x3 <-
      x2 |>
      px_language("en") |>
      px_languages(c("en", "kl"))

    individual_keywords_ml <-
      tibble::tribble(
        ~variable, ~language, ~px_description, ~px_matrix,
        "age", "en", "Age count 18-99", "AGE",
        "age", "kl", "Ukiut 18-99", NA,
        "gender", "en", "Gender count", "GEN",
        "gender", "kl", " Suiaassuseq", NA,
        "municipality", "en", "Municipality 2024", "MUN",
        "municipality", "kl", "Kommuni 2024", NA
      )

    px_micro(x3, out_dir = micro_dir, keyword_values = individual_keywords_ml)

Here ‘px_description’ varies for each language, and ‘px_matrix’ is only set for one of the languages, since it is not a language dependent keywords. For language independant keywords it doesn’t matter which language the value is set for.

### Filenames

The filenames of the micro files are by default the name of the variable, however these can also be changed by passing a ‘filename’ column to ‘keyword_values’

    individual_keywords2 <-
      individual_keywords |>
      dplyr::mutate(filename = paste0(variable, "_2024", ".px"))

    # Clear folder
    unlink(file.path(micro_dir, "*.px"))

    px_micro(x2, out_dir = micro_dir, keyword_values = individual_keywords2)

    list.files(micro_dir)
    #> [1] "age_2024.px"          "gender_2024.px"       "municipality_2024.px"