# Reading REDATAM files in R

We start by downloading the Chilean Census 2017 from ECLAC website (link valid as of 2024-10-01):

    url <- "https://redatam.org/cdr/descargas/censos/poblacion/CP2017CHL.zip"
    zip <- "CP2017CHL.zip"

    if (!file.exists(zip)) {
      download.file(url, zip, method = "wget")
    }

Now we can extract the files:

    # install.packages("archive")
    dout <- basename(zip)
    dout <- sub("\\.zip$", "", dout)
    archive::archive_extract(zip, dir = dout)

You can use `unzip()` from base R, but this file in particular gave me an error. The `archive` package is a wrapper around ‘libarchive’ that provides multi-format archive and compression support.

The REDATAM files are now stored in the `CP2017CHL` directory. We can read the REDATAM dictionary file (DIC or DICX for this particular case):

    library(redatam)

    fout <- "chile2017.rds"

    if (!file.exists(fout)) {
      chile2017 <- read_redatam("CP2017CHL/BaseOrg16/CPV2017-16.dicx")
      saveRDS(chile2017, fout)
    } else {
      chile2017 <- readRDS(fout)
    }

One of the many possibilities with this census is to obtain the number of houses with overcrowding. For this, the Secretary for Social Development and Family (Ministerio de Desarrollo Social y Familia) divides the number of people residing in a dwelling and the number of bedrooms in the dwelling, with the special case of adding one to studio apartments and similar units, and the result is discretized as follows.

- No overcrowding \([0,2.5)\)
- Mean \([2.5,3.5)\)
- High \([3.5,4.9)\)
- Critical \([5,Inf)\)

According to the census documentation in the previous ZIP file, this consists in dividing the variables `cant_pers` and `p04` from the `vivienda` (housing) table to then discretize the result. The documentation also states that we must join the `vivienda` table with `zonaloc` (zones), `area`, `distrito` (district) and `communa` (municipality) to match each house with its corresponding municipality. This can be done with `dplyr`:

    library(dplyr)

    overcrowding <- chile2017$comuna %>%
      select(ncomuna, comuna_ref_id) %>%
      inner_join(
        chile2017$distrito %>%
        select(distrito_ref_id, comuna_ref_id)
      ) %>%
      inner_join(
        chile2017$area %>%
          select(area_ref_id, distrito_ref_id)
      ) %>%
      inner_join(
        chile2017$zonaloc %>%
          select(zonaloc_ref_id, area_ref_id)
      ) %>%
      inner_join(
        chile2017$vivienda %>%
          select(zonaloc_ref_id, vivienda_ref_id, cant_per, p04) %>%
          mutate(
            p04 = case_when(
              p04 == 98 ~ NA_integer_,
              p04 == 99 ~ NA_integer_,
              TRUE ~ p04
            )
          ) %>%
          filter(!is.na(p04))
      ) %>%
      mutate(
        overcrowding = case_when(
          p04 >=1 ~ cant_per / p04,
          p04 ==0 ~ cant_per / (p04 + 1)
        )
      ) %>%
      mutate(
        overcrowding_discrete = case_when(
          overcrowding  < 2.5                      ~ "No Overcrowding",
          overcrowding >= 2.5 & overcrowding < 3.5 ~ "Mean",
          overcrowding >= 3.5 & overcrowding < 5   ~ "High",
          overcrowding >= 5                        ~ "Critical"
        )
      ) %>%
      group_by(comuna = ncomuna, overcrowding_discrete) %>%
      count()

Now we can filter for any municipality of our interest, for example:

    overcrowding %>%
      filter(comuna == "VITACURA")

    overcrowding %>%
      filter(comuna == "LA PINTANA")

    # A tibble: 4 × 3
    # Groups:   comuna, overcrowding_discrete [4]
      comuna   overcrowding_discrete     n
      <fct>    <chr>                 <int>
    1 VITACURA Critical                  9
    2 VITACURA High                     18
    3 VITACURA Mean                    174
    4 VITACURA No Overcrowding       26752

    # A tibble: 4 × 3
    # Groups:   comuna, overcrowding_discrete [4]
      comuna     overcrowding_discrete     n
      <fct>      <chr>                 <int>
    1 LA PINTANA Critical                497
    2 LA PINTANA High                   1112
    3 LA PINTANA Mean                   4522
    4 LA PINTANA No Overcrowding       39163