fasstr: calc_flow_percentile – R documentation

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calc_flow_percentile

Calculate the percentile rank of a flow value

Description

Calculates the percentile rank of a discharge value compared to all flow values of a streamflow data set. Looks up the value in the distribution (stats::ecdf() function) of all daily discharge values from all years, unless specified. Returns a tibble with statistics.

Usage

calc_flow_percentile(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  roll_days = 1,
  roll_align = "right",
  flow_value,
  water_year_start = 1,
  start_year,
  end_year,
  exclude_years,
  complete_years = FALSE,
  months = 1:12
)

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.
`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'`.
`flow_value`	A numeric flow value of which to determine the percentile rank. Required.
`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.
`complete_years`	Logical values indicating whether to include only years with complete data in analysis. Default `FALSE`.
`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`).

Value

A tibble data frame, or a single numeric value if no station number provided, of the percentile rank of a given flow value.

Examples

# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {

# Calculate the percentile rank of a 10-cms flow value from a full record
calc_flow_percentile(station_number = "08NM116", 
                     flow_value = 10)

# Calculate the percentile rank of a 10-cms flow value from years with no missing data
calc_flow_percentile(station_number = "08NM116", 
                     complete_years = TRUE,
                     flow_value = 10)
                     
# Calculate the percentile rank of a 10-cms flow value for June from years with no missing data
calc_flow_percentile(station_number = "08NM116", 
                     complete_years = TRUE,
                     months = 6,
                     flow_value = 10)
                     
}

fasstr

Analyze, Summarize, and Visualize Daily Streamflow Data

v0.3.2

Apache License 2.0

Authors

Jon Goetz [aut, cre] (<https://orcid.org/0000-0002-4993-1119>), Carl James Schwarz [aut], Robin Pike [ctb], Province of British Columbia [cph]

Initial release