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, ignore_missing = FALSE )
data  Data frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers).
Leave blank if using 

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 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. 
transpose  Logical value indicating whether to transpose rows and columns of results. Default 
ignore_missing  Logical value indicating whether dates with missing values should be included in the calculation. If

A tibble data frame with the following columns:
calendar or water year selected
annual minimum for each nday rolling mean, direction of mean specified by roll_align
day of year for each annual minimum of nday rolling mean
date (YYYYMMDD) for each annual minimum of nday rolling mean
annual 1day mean minimum (roll_align = right)
day of year of annual 1day mean minimum
date (YYYYMMDD) of annual 1day mean minimum
annual 3day mean minimum (roll_align = right)
day of year of annual 3day mean minimum
date (YYYYMMDD) of annual 3day mean minimum
annual 7day mean minimum (roll_align = right)
day of year of annual 7day mean minimum
date (YYYYMMDD) of annual 7day mean minimum
annual 30day mean minimum (roll_align = right)
day of year of annual 30day mean minimum
date (YYYYMMDD) of annual 30day mean minimum
# 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") }#> 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 Min_7_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: Min_7_Day_DoY <dbl>, #> # Min_7_Day_Date <date>