`R/calc_annual_normal_days.R`

`calc_annual_normal_days.Rd`

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_normal_days(
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
)
```

- 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

`NULL`

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 or set to`NULL`

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 or set well before start date (i.e.

`1800`

) to use from the first year of the source data.- end_year
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.- exclude_years
Numeric vector of years to exclude from analysis. Leave blank or set to

`NULL`

to include all years.- months
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`

).- transpose
Logical value indicating whether to transpose rows and columns of results. Default

`FALSE`

.

A tibble data frame with the following columns:

- Year
calendar or water year selected

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

- Above_Normal_Days
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.

```
# 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_normal_days(station_number = "08NM116")
# Calculate statistics with custom limits of normal
calc_annual_normal_days(station_number = "08NM116",
normal_percentiles = c(10,90),
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.
#> # A tibble: 41 × 5
#> STATION_NUMBER Year Normal_Days Below_Normal_Days Above_Normal_Days
#> <chr> <dbl> <int> <int> <int>
#> 1 08NM116 1980 328 24 14
#> 2 08NM116 1981 289 3 73
#> 3 08NM116 1982 253 14 98
#> 4 08NM116 1983 263 0 102
#> 5 08NM116 1984 306 9 51
#> 6 08NM116 1985 300 51 14
#> 7 08NM116 1986 339 8 18
#> 8 08NM116 1987 188 169 8
#> 9 08NM116 1988 222 128 16
#> 10 08NM116 1989 332 21 12
#> # … with 31 more rows
```