# Quality Control of SHARK Data

## Overview

The SHARK4R package provides a set of functions to perform quality control (QC) on SHARK data. These functions help identify missing or invalid values, spatial errors, and statistical outliers and are mainly intended for internal data validation. The tutorial covers:

- Field validation (required and datatype-specific fields)
- Code validation (project and platform codes)
- Geospatial checks (points on land, basins, proximity to shore)
- Depth checks (missing, negative, or implausible values)
- Outlier detection (parameter-specific thresholds)
- Logical Parameter Checks (parameter-specific rules)
- Interactive QC with a Shiny app

This workflow ensures SHARK data are consistent, valid, and ready for analysis. Several quality control components, originally developed by Provoost and Bosch (2024), have been adapted for compatibility with the SHARK format.

## Installation

You can install the latest version of `SHARK4R` from CRAN using:

    install.packages("SHARK4R")

Load the package along with `dplyr`:

    library(SHARK4R)

## Retrieve SHARK Data

You can fetch SHARK data using the same filtering options as the SHARK web interface. Explore available options with:

    shark_options <- get_shark_options()

Filter datasets containing “Chlorophyll”:

    # Filter names using grepl
    chlorophyll_datasets <- shark_options$datasets[grepl("Chlorophyll",
                                                         shark_options$datasets)]

    # Select the first dataset for demonstration
    selected_dataset <- chlorophyll_datasets[1]

    # Print the name of the selected dataset
    print(selected_dataset)

    ## [1] "SHARK_Chlorophyll_1985_1989_SMHI_version_2023-04-27.zip"

Download the selected dataset as a data frame:

    chlorophyll_data <- get_shark_datasets(selected_dataset,
                                           save_dir = tempdir(),
                                           return_df = TRUE,
                                           verbose = FALSE)

    print(chlorophyll_data)

    ## # A tibble: 80 × 73
    ##    source delivery_datatype check_status_sv data_checked_by_sv visit_year
    ##     <dbl> <chr>             <chr>           <chr>                   <dbl>
    ##  1      1 Chlorophyll       Klar            Leverantör               1989
    ##  2      1 Chlorophyll       Klar            Leverantör               1989
    ##  3      1 Chlorophyll       Klar            Leverantör               1985
    ##  4      1 Chlorophyll       Klar            Leverantör               1989
    ##  5      1 Chlorophyll       Klar            Leverantör               1989
    ##  6      1 Chlorophyll       Klar            Leverantör               1989
    ##  7      1 Chlorophyll       Klar            Leverantör               1989
    ##  8      1 Chlorophyll       Klar            Leverantör               1989
    ##  9      1 Chlorophyll       Klar            Leverantör               1989
    ## 10      1 Chlorophyll       Klar            Leverantör               1989
    ## # ℹ 70 more rows
    ## # ℹ 68 more variables: visit_month <dbl>, station_name <chr>,
    ## #   reported_station_name <chr>, sample_location_id <dbl>, station_id <dbl>,
    ## #   sample_project_name_en <chr>, sample_orderer_name_en <chr>,
    ## #   platform_code <chr>, visit_id <dbl>, expedition_id <lgl>,
    ## #   shark_sample_id_md5 <chr>, sample_date <date>, sample_time <time>,
    ## #   sample_enddate <lgl>, sample_endtime <lgl>, sample_latitude_dm <chr>, …

SHARK data can be downloaded and saved locally using the `save_dir` argument, then imported into R using the function `read_shark()` for both ZIP archives or text files.

## Step 1: Check Required Fields

Validate mandatory fields:

- Global fields: `check_datatype()`
- Datatype-specific fields: `check_fields()` with optional `field_definitions`

    check_fields(data = chlorophyll_data, datatype = "Chlorophyll")

    ## # A tibble: 1,195 × 4
    ##    level field                           row message
    ##    <chr> <chr>                         <int> <chr>
    ##  1 error sample_project_name_sv           NA Required field sample_project_name…
    ##  2 error sample_orderer_name_sv           NA Required field sample_orderer_name…
    ##  3 error sampling_laboratory_name_sv      NA Required field sampling_laboratory…
    ##  4 error analytical_laboratory_name_sv    NA Required field analytical_laborato…
    ##  5 error reporting_institute_name_sv      NA Required field reporting_institute…
    ##  6 error sample_enddate                    1 Empty value for required field sam…
    ##  7 error sample_enddate                    2 Empty value for required field sam…
    ##  8 error sample_enddate                    3 Empty value for required field sam…
    ##  9 error sample_enddate                    4 Empty value for required field sam…
    ## 10 error sample_enddate                    5 Empty value for required field sam…
    ## # ℹ 1,185 more rows

## Step 2: Validate Project and Platform Codes

Ensure metadata codes follow SHARK conventions:

    # Validate project codes
    check_codes(chlorophyll_data)

    ## All PROJ codes found

    ## # A tibble: 1 × 2
    ##   reported_code              match_type
    ##   <chr>                      <lgl>
    ## 1 National marine monitoring TRUE

    # Validate ship/platform codes
    check_codes(data = chlorophyll_data,
                field = "platform_code",
                code_type = "SHIPC",
                match_column = "Code")

    ## All SHIPC codes found

    ## # A tibble: 2 × 2
    ##   reported_code match_type
    ##   <chr>         <lgl>
    ## 1 77AR          TRUE
    ## 2 77SN          TRUE

## Step 3: Geospatial Checks

### Visualize Data Points

    plot_map_leaflet(chlorophyll_data)

    ## The interactive map is omitted here but appears in the online tutorial.

### Identify Points on Land

    n_rows_on_land <- check_onland(chlorophyll_data)
    nrow(n_rows_on_land)

    ## [1] 0

Optional geospatial QC functions:

- `positions_are_near_land()`
- `which_basin()` from the iRfcb package

## Step 4: Depth Checks

Verify plausibility and consistency of depth values:

    check_depth(data = chlorophyll_data) # default columns: min/max depth

    ## # A tibble: 2 × 4
    ##   level     row field              message
    ##   <chr>   <int> <chr>              <chr>
    ## 1 warning    17 sample_max_depth_m Depth value (20) is greater than the value f…
    ## 2 warning    80 sample_max_depth_m Depth value (20) is greater than the value f…

    check_depth(data = chlorophyll_data, "water_depth_m")

    ## # A tibble: 57 × 4
    ##    level     row field         message
    ##    <chr>   <int> <chr>         <chr>
    ##  1 warning     2 water_depth_m Depth value (78) is greater than the value found…
    ##  2 warning     3 water_depth_m Depth value (78) is greater than the value found…
    ##  3 warning     4 water_depth_m Depth value (637) is greater than the value foun…
    ##  4 warning     6 water_depth_m Depth value (86) is greater than the value found…
    ##  5 warning     8 water_depth_m Depth value (25) is greater than the value found…
    ##  6 warning     9 water_depth_m Depth value (41) is greater than the value found…
    ##  7 warning    10 water_depth_m Depth value (90) is greater than the value found…
    ##  8 warning    11 water_depth_m Depth value (74) is greater than the value found…
    ##  9 warning    13 water_depth_m Depth value (465) is greater than the value foun…
    ## 10 warning    14 water_depth_m Depth value (465) is greater than the value foun…
    ## # ℹ 47 more rows

Checks performed:

- Missing depth column or empty values (warnings)
- Non-numeric or negative values (errors)
- Depth exceeding bathymetry or minimum > maximum (errors)

## Step 5: Outlier Detection

Retrieve reference statistics for your datatype:

    shark_statistics <- get_shark_statistics(datatype = "Chlorophyll",
                                             fromYear = 2020,
                                             toYear = 2024,
                                             verbose = FALSE)

    print(shark_statistics)

    ## # A tibble: 1 × 24
    ##   parameter  datatype fromYear toYear     n   min    Q1 median    Q3   max   P01
    ##   <chr>      <chr>       <dbl>  <dbl> <int> <dbl> <dbl>  <dbl> <dbl> <dbl> <dbl>
    ## 1 Chlorophy… Chlorop…     2020   2024  1374  0.19  1.39    2.2   3.3  22.2 0.307
    ## # ℹ 13 more variables: P05 <dbl>, P95 <dbl>, P99 <dbl>, IQR <dbl>, mean <dbl>,
    ## #   sd <dbl>, var <dbl>, cv <dbl>, mad <dbl>, mild_lower <dbl>,
    ## #   mild_upper <dbl>, extreme_lower <dbl>, extreme_upper <dbl>

Detect extreme values using thresholds (e.g., 99th percentile):

    check_outliers(data = chlorophyll_data,
                   parameter = "Chlorophyll-a",
                   datatype = "Chlorophyll",
                   threshold_col = "P99",
                   thresholds = shark_statistics)

    ## Chlorophyll-a is within the P99 range.

Visualize anomalies:

    # Scatterplot with horizontal line at 99th percentile
    scatterplot(chlorophyll_data,
                hline = shark_statistics$P99)

    ## The interactive plot is omitted here but appears in the online tutorial.

## Step 6: Logical Parameter Checks

Use `check_parameter_rules()` to flag measurements that violate parameter-specific or row-wise logical rules.

    check_parameter_rules(data = chlorophyll_data)

    ## No parameters from the logical rules are present in the dataset. Available parameters are: Total cover of all species, Cover, Cover class, Sediment deposition cover, Abundance class, Wet weight

- `return_df = TRUE` gives a data frame of violations.
- `return_logical = TRUE` gives logical vectors for each parameter.
- Only parameters present in the dataset are checked; available parameters are listed if none match.
- You can define custom rules by providing your own `param_conditions` or `rowwise_conditions` lists.

## Step 7: Station Matching

Verify station names against the official SHARK registry:

    station_match <- match_station(chlorophyll_data$station_name)

    ## Using station.txt from NODC_CONFIG: /home/anders/nodc_config//nodc_station/station.txt

    ## All stations found

    head(station_match)

    ##   reported_station_name match_type
    ## 1            425 GNIBEN       TRUE
    ## 2                FLADEN       TRUE
    ## 3                FLADEN       TRUE
    ## 4                    M6       TRUE
    ## 5              ANHOLT E       TRUE
    ## 6              W SKAGEN       TRUE

To plot stations and their distances from the station register in an interactive map:

    check_station_distance(data = chlorophyll_data,
                           plot_leaflet = TRUE)

    ## The interactive map is omitted here but appears in the online tutorial.

To check if stations are nominal (comparing unique coordinates per station):

    check_nominal_station(data = chlorophyll_data)

    ## Positions are not suspected to be nominal

## Interactive QC with Shiny

For a more user-friendly interface, use the Shiny QC app:

    # Run the app
    run_qc_app()

    # Alternative, download support files and knit documents locally
    check_setup(path = tempdir()) # using a temp folder in this example

The app provides point-and-click access to the same QC checks described above.

## Recommended Workflow Summary

1. Check Required Fields (`check_datatype()`, `check_fields()`)
2. Validate Codes (`check_codes()`)
3. Geospatial Checks (`plot_map_leaflet()`, `check_onland()`, optional `positions_are_near_land()`, `which_basin()`)
4. Depth Checks (`check_depth()`)
5. Outlier Detection (`check_outliers()`, `scatterplot()`)
6. Logical Parameter Checks (`check_parameter_rules()`)
7. Station Matching (`match_station()`)
8. Final Review & Visualization (interactive maps and scatterplots)

Following this order ensures comprehensive QC and prepares your SHARK data for analysis.

## Citation

    ## To cite package 'SHARK4R' in publications use:
    ##
    ##   Lindh, M. and Torstensson, A. (2026). SHARK4R: Accessing and
    ##   Validating Marine Environmental Data from 'SHARK' and Related
    ##   Databases. R package version 1.1.0.
    ##   https://CRAN.R-project.org/package=SHARK4R
    ##
    ## A BibTeX entry for LaTeX users is
    ##
    ##   @Manual{,
    ##     title = {SHARK4R: Accessing and Validating Marine Environmental Data from 'SHARK' and Related Databases},
    ##     author = {Markus Lindh and Anders Torstensson},
    ##     year = {2026},
    ##     note = {R package version 1.1.0},
    ##     url = {https://CRAN.R-project.org/package=SHARK4R},
    ##   }

## References

- Provoost P, Bosch S (2024). `obistools`: Tools for data enhancement and quality control. Ocean Biodiversity Information System. Intergovernmental Oceanographic Commission of UNESCO. R package version 0.1.0, https://iobis.github.io/obistools/.