Calculates the number of days per year outside of the 'normal' range (typically between 25 and 75th percentiles) for each day of the year. Upper and lower-range percentiles are calculated for each day of the year of from all years, and then each daily flow value for each year is compared. All days above or below the normal range are included. Analysis methodology is based on Environment and Climate Change Canada's Water Quantity indicator from the Canadian Environmental Sustainability Indicators. Calculates statistics from all values from complete years, unless specified. Returns a tibble with statistics.

calc_annual_outside_normal(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  normal_percentiles = c(25, 75),
  roll_days = 1,
  roll_align = "right",
  water_year_start = 1,
  start_year,
  end_year,
  exclude_years,
  months = 1:12,
  transpose = 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.

normal_percentiles

Numeric vector of two values, lower and upper percentiles, respectively indicating the limits of the normal range. Default c(25,75).

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.

Value

A tibble data frame with the following columns:

Year

calendar or water year selected

Days_Below_Normal

number of days per year below the daily normal (default 25th percentile)

Days_Above_Normal

number of days per year above the daily normal (default 75th percentile)

Days_Outside_Normal

number of days per year below and above the daily normal (default 25/75th percentile)

Transposing data creates a column of "Statistics" and subsequent columns for each year selected.

Examples

# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat()) if (file.exists(tidyhydat::hy_downloaded_db())) { # Calculate statistics with default limits of normal (25 and 75th percentiles) calc_annual_outside_normal(station_number = "08NM116") # Calculate statistics with custom limits of normal calc_annual_outside_normal(station_number = "08NM116", normal_percentiles = c(10,90)) }
#> 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 5 #> STATION_NUMBER Year Days_Below_Normal Days_Above_Normal Days_Outside_Normal #> <chr> <dbl> <int> <int> <int> #> 1 08NM116 1949 NA NA NA #> 2 08NM116 1950 NA NA NA #> 3 08NM116 1951 NA NA NA #> 4 08NM116 1952 NA NA NA #> 5 08NM116 1953 NA NA NA #> 6 08NM116 1954 NA NA NA #> 7 08NM116 1955 NA NA NA #> 8 08NM116 1956 NA NA NA #> 9 08NM116 1957 NA NA NA #> 10 08NM116 1958 NA NA NA #> # ... with 59 more rows