View source: R/calc_annual_lowflows.R
calc_annual_lowflows  R Documentation 
Calculates annual nday minimum 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_lowflows(
data,
dates = Date,
values = Value,
groups = STATION_NUMBER,
station_number,
roll_days = c(1, 3, 7, 30),
roll_align = "right",
water_year_start = 1,
start_year,
end_year,
exclude_years,
months = 1:12,
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_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, 
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 each nday rolling mean, direction of mean specified by roll_align 
Min_'n'_Day_DoY 
day of year for each annual minimum of nday rolling mean 
Min_'n'_Day_Date 
date (YYYYMMDD) for each annual minimum 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 
Min_3_Day 
annual 3day mean minimum (roll_align = right) 
Min_3_Day_DoY 
day of year of annual 3day mean minimum 
Min_3_Day_Date 
date (YYYYMMDD) of annual 3day mean minimum 
Min_7_Day 
annual 7day mean minimum (roll_align = right) 
Min_7_Day_DoY 
day of year of annual 7day mean minimum 
Min_7_Day_Date 
date (YYYYMMDD) of annual 7day mean minimum 
Min_30_Day 
annual 30day mean minimum (roll_align = right) 
Min_30_Day_DoY 
day of year of annual 30day mean minimum 
Min_30_Day_Date 
date (YYYYMMDD) of annual 30day mean minimum 
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 1, 3, 7, and 30day (default) low flows with
# default alignment ('right')
calc_annual_lowflows(station_number = "08NM116")
# Calculate custom 3 and 7day annual low flows with 'center' alignment
calc_annual_lowflows(station_number = "08NM116",
roll_days = c(3,7),
roll_align = "center",
start_year = 1980)
}
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