Calculate annual peak flows

Calculates annual n-day minimum and maximum values, and the day of year and date of occurrence of daily flow values from a daily streamflow data set. Calculates statistics from all values, unless specified. Returns a tibble with statistics.

calc_annual_peaks(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  roll_days = 1,
  roll_align = "right",
  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'.
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

Min_'n'_Day

annual minimum for selected n-day rolling mean, direction of mean specified by roll_align

Min_'n'_Day_DoY

day of year for selected annual minimum of n-day rolling mean

Min_'n'_Day_Date

date (YYYY-MM-DD) for selected annual minimum of n-day rolling mean

Max_'n'_Day

annual maximum for selected n-day rolling mean, direction of mean specified by roll_align

Max_'n'_Day_DoY

day of year for selected annual maximum of n-day rolling mean

Max_'n'_Day_Date

date (YYYY-MM-DD) for selected annual maximum of n-day rolling mean

Default columns:

Min_1_Day

annual 1-day mean minimum (roll_align = right)

Min_1_Day_DoY

day of year of annual 1-day mean minimum

Min_1_Day_Date

date (YYYY-MM-DD) of annual 1-day mean minimum

Max_1_Day

annual 1-day mean maximum (roll_align = right)

Max_1_Day_DoY

day of year of annual 1-day mean maximum

Max_1_Day_Date

date (YYYY-MM-DD) of annual 1-day mean maximum

Transposing data creates a column of 'Statistics' and subsequent columns for each year selected. 'Date' statistics not transposed.

Examples

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

# Calculate annual 1-day (default) peak flow data with 
# default alignment ('right')
calc_annual_peaks(station_number = "08NM116") 

# Calculate custom 3-day peak flow data with 'center' alignment
calc_annual_peaks(station_number = "08NM116",
                  roll_days = 3,
                  roll_align = "center")
                     
}
#> 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 Min_3_Day Min_3_Day_DoY Min_3_Day_Date Max_3_Day
#>    <chr>          <dbl>     <dbl>         <dbl> <date>             <dbl>
#>  1 08NM116         1949        NA            NA NA                    NA
#>  2 08NM116         1950        NA            NA NA                    NA
#>  3 08NM116         1951        NA            NA NA                    NA
#>  4 08NM116         1952        NA            NA NA                    NA
#>  5 08NM116         1953        NA            NA NA                    NA
#>  6 08NM116         1954        NA            NA NA                    NA
#>  7 08NM116         1955        NA            NA NA                    NA
#>  8 08NM116         1956        NA            NA NA                    NA
#>  9 08NM116         1957        NA            NA NA                    NA
#> 10 08NM116         1958        NA            NA NA                    NA
#> # ... with 59 more rows, and 2 more variables: Max_3_Day_DoY <dbl>,
#> #   Max_3_Day_Date <date>