Calculates annual n-day 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 frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers).
Leave blank or set to NULL if using station_number argument.
Name of column in data that contains dates formatted YYYY-MM-DD. Only required if dates column name is not
'Date' (default). Leave blank or set to NULL if using station_number argument.
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.
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.
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.
Numeric value of the number of days to apply a rolling mean. Default 1.
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'.
Numeric value indicating the month (1 through 12) of the start of water year for
analysis. Default 1.
Numeric value of the first year to consider for analysis. Leave blank or set well before start date (i.e.
1800) to use from the first year of the source data.
Numeric value of the last year to consider for analysis. Leave blank or set well after end date (i.e.
2100) to use up to the last year of the source data.
Numeric vector of years to exclude from analysis. Leave blank or set to NULL to include all years.
Numeric vector of months to include in analysis. For example, 3 for March, 6:8 for Jun-Aug or
c(10:12,1) for first four months (Oct-Jan) when water_year_start = 10 (Oct). Default summarizes all
months (1:12).
Logical value indicating whether to transpose rows and columns of results. Default FALSE.
Logical values indicating whether to include only years with complete data in analysis. Default FALSE.
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.
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 'ignore_missing = FALSE' then it defaults to 0 (zero missing dates allowed),
if 'ignore_missing = TRUE' then it defaults to 100 (any missing dates allowed); consistent with
ignore_missing usage. Supersedes ignore_missing when used.
A tibble data frame with the following columns:
calendar or water year selected
annual minimum for each n-day rolling mean, direction of mean specified by roll_align
day of year for each annual minimum of n-day rolling mean
date (YYYY-MM-DD) for each annual minimum of n-day rolling mean
Default columns:
annual 1-day mean minimum (roll_align = right)
day of year of annual 1-day mean minimum
date (YYYY-MM-DD) of annual 1-day mean minimum
annual 3-day mean minimum (roll_align = right)
day of year of annual 3-day mean minimum
date (YYYY-MM-DD) of annual 3-day mean minimum
annual 7-day mean minimum (roll_align = right)
day of year of annual 7-day mean minimum
date (YYYY-MM-DD) of annual 7-day mean minimum
annual 30-day mean minimum (roll_align = right)
day of year of annual 30-day mean minimum
date (YYYY-MM-DD) of annual 30-day 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 30-day (default) low flows with
# default alignment ('right')
calc_annual_lowflows(station_number = "08NM116")
# Calculate custom 3 and 7-day annual low flows with 'center' alignment
calc_annual_lowflows(station_number = "08NM116",
roll_days = c(3,7),
roll_align = "center",
start_year = 1980)
}
#> Warning: One or more calculations included missing values and NA's were produced. If desired, filter data for complete years or months, or use the 'ignore_missing' or 'allowed_missing' arguments (if applicable) to ignore or allow some missing values.
#> Warning: One or more calculations included missing values and NA's were produced. If desired, filter data for complete years or months, or use the 'ignore_missing' or 'allowed_missing' arguments (if applicable) to ignore or allow some missing values.
#> # A tibble: 41 × 8
#> STATION_NUMBER Year Min_3_Day Min_3_…¹ Min_3_Da…² Min_7…³ Min_7…⁴ Min_7_Da…⁵
#> <chr> <dbl> <dbl> <dbl> <date> <dbl> <dbl> <date>
#> 1 08NM116 1980 0.632 9 1980-01-09 0.655 7 1980-01-07
#> 2 08NM116 1981 0.468 260 1981-09-17 0.885 258 1981-09-15
#> 3 08NM116 1982 0.883 6 1982-01-06 1.05 5 1982-01-05
#> 4 08NM116 1983 0.562 357 1983-12-23 0.634 357 1983-12-23
#> 5 08NM116 1984 0.742 365 1984-12-30 0.766 366 1984-12-31
#> 6 08NM116 1985 0.429 190 1985-07-09 0.589 189 1985-07-08
#> 7 08NM116 1986 0.663 50 1986-02-19 0.719 49 1986-02-18
#> 8 08NM116 1987 0.339 333 1987-11-29 0.334 365 1987-12-31
#> 9 08NM116 1988 0.150 32 1988-02-01 0.186 33 1988-02-02
#> 10 08NM116 1989 0.524 271 1989-09-28 0.577 270 1989-09-27
#> # … with 31 more rows, and abbreviated variable names ¹Min_3_Day_DoY,
#> # ²Min_3_Day_Date, ³Min_7_Day, ⁴Min_7_Day_DoY, ⁵Min_7_Day_Date