Calculate annual summary statistics — calc_annual

Calculates means, medians, maximums, minimums, and percentiles for each year from all years of a daily streamflow data set. Calculates statistics from all values, unless specified. Returns a tibble with statistics.

calc_annual_stats(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  roll_days = 1,
  roll_align = "right",
  percentiles = c(10, 90),
  water_year_start = 1,
  start_year,
  end_year,
  exclude_years,
  months = 1:12,
  transpose = FALSE,
  ignore_missing = FALSE
)

Arguments

data	Data frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers). Leave blank if using `station_number` argument.
dates	Name of column in `data` that contains dates formatted YYYY-MM-DD. Only required if dates column name is not 'Date' (default). Leave blank if using `station_number` argument.
values	Name of column in `data` that contains numeric flow values, in units of cubic metres per second. Only required if values column name is not 'Value' (default). Leave blank if using `station_number` argument.
groups	Name of column in `data` that contains unique identifiers for different data sets, if applicable. Only required if groups column name is not 'STATION_NUMBER'. Function will automatically group by a column named 'STATION_NUMBER' if present. Remove the 'STATION_NUMBER' column beforehand to remove this grouping. Leave blank if using `station_number` argument.
station_number	Character string vector of seven digit Water Survey of Canada station numbers (e.g. `"08NM116"`) of which to extract daily streamflow data from a HYDAT database. Requires `tidyhydat` package and a HYDAT database. Leave blank if using `data` argument.
roll_days	Numeric value of the number of days to apply a rolling mean. Default `1`.
roll_align	Character string identifying the direction of the rolling mean from the specified date, either by the first (`'left'`), last (`'right'`), or middle (`'center'`) day of the rolling n-day group of observations. Default `'right'`.
percentiles	Numeric vector of percentiles to calculate. Set to `NA` if none required. Default `c(10,90)`.
water_year_start	Numeric value indicating the month (`1` through `12`) of the start of water year for analysis. Default `1`.
start_year	Numeric value of the first year to consider for analysis. Leave blank to use the first year of the source data.
end_year	Numeric value of the last year to consider for analysis. Leave blank to use the last year of the source data.
exclude_years	Numeric vector of years to exclude from analysis. Leave blank to include all years.
months	Numeric vector of months to include in analysis (e.g. `6:8` for Jun-Aug). Leave blank to summarize all months (default `1:12`).
transpose	Logical value indicating whether to transpose rows and columns of results. Default `FALSE`.
ignore_missing	Logical value indicating whether dates with missing values should be included in the calculation. If `TRUE` then a statistic will be calculated regardless of missing dates. If `FALSE` then only those statistics from time periods with no missing dates will be returned. Default `FALSE`.

Value

A tibble data frame with the following columns:

Year

calendar or water year selected

Mean

annual mean of all daily flows for a given year

Median

annual median of all daily flows for a given year

Maximum

annual maximum of all daily flows for a given year

Minimum

annual minimum of all daily flows for a given year

P'n'

each annual n-th percentile selected of all daily flows

Default percentile columns:

P10

annual 10th percentile of all daily flows for a given year

P90

annual 90th percentile of all daily flows for a given year

Transposing data creates a column of "Statistics" and subsequent columns for each year selected.

Examples

# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {

# Calculate annual statistics from a data frame using the data argument
flow_data <- tidyhydat::hy_daily_flows(station_number = "08NM116")
calc_annual_stats(data = flow_data)

# Calculate annual statistics using station_number argument
calc_annual_stats(station_number = "08NM116")

# Calculate annual statistics regardless if there 
# is missing data for a given year
calc_annual_stats(station_number = "08NM116",
                  ignore_missing = TRUE)
                  
# Calculate annual statistics for water years starting in October
calc_annual_stats(station_number = "08NM116",
                  water_year_start = 10)
                  
# Calculate annual statistics filtered for custom years
calc_annual_stats(station_number = "08NM116",
                  start_year = 1981,
                  end_year = 2010,
                  exclude_years = c(1991,1993:1995))
                  
# Calculate annual statistics for 7-day flows for July-September 
# months only, with 25 and 75th percentiles
calc_annual_stats(station_number = "08NM116",
                  roll_days = 7,
                  months = 7:9,
                  percentiles = c(25,75))
                  
}
#> Warning: One or more calculations included missing values and NA's were produced. Filter data for complete years or months, or use to ignore_missing = TRUE to ignore missing values.
#> Warning: One or more calculations included missing values and NA's were produced. Filter data for complete years or months, or use to ignore_missing = TRUE to ignore missing values.
#> Warning: One or more calculations included missing values and NA's were produced. Filter data for complete years or months, or use to ignore_missing = TRUE to ignore missing values.
#> Warning: One or more calculations included missing values and NA's were produced. Filter data for complete years or months, or use to ignore_missing = TRUE to ignore missing values.
#> # A tibble: 69 x 8
#>    STATION_NUMBER  Year  Mean Median Maximum Minimum   P25   P75
#>    <chr>          <dbl> <dbl>  <dbl>   <dbl>   <dbl> <dbl> <dbl>
#>  1 08NM116         1949  1.52   1.32    4.29   0.838 1.09   1.64
#>  2 08NM116         1950  2.71   1.36   16.6    0.714 0.860  2.10
#>  3 08NM116         1951  2.21   1.23    8.80   0.629 0.758  2.01
#>  4 08NM116         1952  2.85   1.93   12.9    1.11  1.32   2.56
#>  5 08NM116         1953  4.77   2.24   24.1    0.821 1.32   7.29
#>  6 08NM116         1954  7.65   4.34   30.5    1.98  3.14   8.88
#>  7 08NM116         1955  4.82   2.35   19.9    0.396 1.21   4.97
#>  8 08NM116         1956  2.25   1.29    8.21   0.784 0.998  2.33
#>  9 08NM116         1957  2.36   1.92    6.23   0.916 1.29   2.84
#> 10 08NM116         1958  1.71   1.23    5.51   0.578 0.880  2.04
#> # ... with 59 more rows