Calculates the timing (day of year and date) of portions of total annual flow of daily flow values from a daily streamflow data set. Calculates statistics from all values from complete years, unless specified. Returns a tibble with statistics.

```
calc_annual_flow_timing(
data,
dates = Date,
values = Value,
groups = STATION_NUMBER,
station_number,
percent_total = c(25, 33.3, 50, 75),
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.- percent_total
Numeric vector of percents of total annual flows to determine dates. Default

`c(25,33.3,50,75)`

.- 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

- DoY_'n'pct_TotalQ
day of year for each n-percent of total volumetric discharge

- Date_'n'pct_TotalQ
date (YYYY-MM-DD) for each n-percent of total volumetric discharge

Default columns:

- DoY_25pct_TotalQ
day of year of 25-percent of total volumetric discharge

- Date_25pct_TotalQ
date (YYYY-MM-DD) of 25-percent of total volumetric discharge

- DoY_33.3pct_TotalQ
day of year of 33.3-percent of total volumetric discharge

- Date_33.3pct_TotalQ
date (YYYY-MM-DD) of 33.3-percent of total volumetric discharge

- DoY_50pct_TotalQ
day of year of 50-percent of total volumetric discharge

- Date_50pct_TotalQ
date (YYYY-MM-DD) of 50-percent of total volumetric discharge

- DoY_75pct_TotalQ
day of year of 75-percent of total volumetric discharge

- Date_75pct_TotalQ
date (YYYY-MM-DD) of 75-percent of total volumetric discharge

Transposing data creates a column of 'Statistics' (just DoY, not Date values) and subsequent columns for each year selected.

Barnett, T.P., Pierce, D.W., Hidalgo, H.G., Bonfils, C., Santer, B.D., Das, T., Bala, G., Wood, A.W., Nozawa, T., Mirin, A.A., Cayan, D.R., Dettinger, M.D., 2008. Human-Induced Clanges in the Hydrology of the Western United States. Science 319, 1080-1083.

```
# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {
# Calculate annual flow timings with default percent of annual totals
calc_annual_flow_timing(station_number = "08NM116")
# Calculate annual flow timings with custom percent of annual totals
calc_annual_flow_timing(station_number = "08NM116",
percent_total = 50)
}
#> 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: 72 × 4
#> STATION_NUMBER Year DoY_50pct_TotalQ Date_50pct_TotalQ
#> <chr> <dbl> <dbl> <date>
#> 1 08NM116 1949 NA NA
#> 2 08NM116 1950 NA NA
#> 3 08NM116 1951 NA NA
#> 4 08NM116 1952 NA NA
#> 5 08NM116 1953 NA NA
#> 6 08NM116 1954 NA NA
#> 7 08NM116 1955 NA NA
#> 8 08NM116 1956 NA NA
#> 9 08NM116 1957 NA NA
#> 10 08NM116 1958 NA NA
#> # … with 62 more rows
```