View source: R/calc_annual_extremes.R
calc_annual_extremes  R Documentation 
Calculates annual nday 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_extremes(
data,
dates = Date,
values = Value,
groups = STATION_NUMBER,
station_number,
roll_days = 1,
roll_days_min = NA,
roll_days_max = NA,
roll_align = "right",
water_year_start = 1,
start_year,
end_year,
exclude_years,
months = 1:12,
months_min = NA,
months_max = NA,
transpose = FALSE,
complete_years = FALSE,
ignore_missing = FALSE,
allowed_missing = ifelse(ignore_missing, 100, 0)
)
data 
Data frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers).
Leave blank or set to 
dates 
Name of column in 
values 
Name of column in 
groups 
Name of column in 
station_number 
Character string vector of seven digit Water Survey of Canada station numbers (e.g. 
roll_days 
Numeric value of the number of days to apply a rolling mean. Default 
roll_days_min 
Numeric value of the number of days to apply a rolling mean for low flows. Will override 'roll_days' argument
for low flows. Default 
roll_days_max 
Numeric value of the number of days to apply a rolling mean for high flows. Will override 'roll_days' argument
for high flows. Default 
roll_align 
Character string identifying the direction of the rolling mean from the specified date, either by the first
( 
water_year_start 
Numeric value indicating the month ( 
start_year 
Numeric value of the first year to consider for analysis. Leave blank or set well before start date (i.e.

end_year 
Numeric value of the last year to consider for analysis. Leave blank or set well after end date (i.e.

exclude_years 
Numeric vector of years to exclude from analysis. Leave blank or set to 
months 
Numeric vector of months to include in analysis. For example, 
months_min 
Numeric vector of specified months for window of low flows (3 for March, 6:8 for JunAug). Will override 'months'
argument for low flows. Default 
months_max 
Numeric vector of specified months for window of high flows (3 for March, 6:8 for JunAug). Will override 'months'
argument for high flows. Default 
transpose 
Logical value indicating whether to transpose rows and columns of results. Default 
complete_years 
Logical values indicating whether to include only years with complete data in analysis. Default 
ignore_missing 
Logical value indicating whether dates with missing values should be included in the calculation. If

allowed_missing 
Numeric value between 0 and 100 indicating the percentage of missing dates allowed to be
included to calculate a statistic (0 to 100 percent). If 
A tibble data frame with the following columns:
Year 
calendar or water year selected 
Min_'n'_Day 
annual minimum for selected nday rolling mean, direction of mean specified by roll_align 
Min_'n'_Day_DoY 
day of year for selected annual minimum of nday rolling mean 
Min_'n'_Day_Date 
date (YYYYMMDD) for selected annual minimum of nday rolling mean 
Max_'n'_Day 
annual maximum for selected nday rolling mean, direction of mean specified by roll_align 
Max_'n'_Day_DoY 
day of year for selected annual maximum of nday rolling mean 
Max_'n'_Day_Date 
date (YYYYMMDD) for selected annual maximum of nday rolling mean 
Default columns:
Min_1_Day 
annual 1day mean minimum (roll_align = right) 
Min_1_Day_DoY 
day of year of annual 1day mean minimum 
Min_1_Day_Date 
date (YYYYMMDD) of annual 1day mean minimum 
Max_1_Day 
annual 1day mean maximum (roll_align = right) 
Max_1_Day_DoY 
day of year of annual 1day mean maximum 
Max_1_Day_Date 
date (YYYYMMDD) of annual 1day mean maximum 
Transposing data creates a column of 'Statistics' and subsequent columns for each year selected. 'Date' statistics not transposed.
# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {
# Calculate annual 1day (default) max/min flow data with
# default alignment ('right')
calc_annual_extremes(station_number = "08NM116")
# Calculate custom 3day max/min flow data with 'center' alignment
calc_annual_extremes(station_number = "08NM116",
roll_days = 3,
roll_align = "center",
start_year = 1980)
}
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