calc_monthly_cumulative_stats: Calculate cumulative monthly flow statistics

Description Usage Arguments Value Examples

View source: R/calc_monthly_cumulative_stats.R

Description

Calculate cumulative monthly flow statistics for each month of the year of daily flow values from a daily streamflow data set. Calculates statistics from all values from complete years, unless specified. Defaults to volumetric cumulative flows, can use use_yield and basin_area to convert to area-based water yield. Returns a tibble with statistics.

Usage

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calc_monthly_cumulative_stats(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  percentiles = c(5, 25, 75, 95),
  use_yield = FALSE,
  basin_area,
  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 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.

percentiles

Numeric vector of percentiles to calculate. Set to NA if none required. Default c(5,25,75,95).

use_yield

Logical value indicating whether to calculate area-based water yield, in mm, instead of volumetric discharge. Default FALSE.

basin_area

Upstream drainage basin area, in square kilometres, to apply to observations. Three options:

(1) Leave blank if groups is STATION_NUMBER with HYDAT station numbers to extract basin areas from HYDAT.

(2) A single numeric value to apply to all observations.

(3) List each basin area for each group/station in groups (can override HYDAT value if listed) as such c("08NM116" = 795, "08NM242" = 10). If group is not listed the HYDAT area will be applied if it exists, otherwise it will be NA.

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). Need to be consecutive months for given year/water year to work properly.

transpose

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

Value

A tibble data frame with the following columns, default units in cubic metres, or millimetres if use_yield and basin_area provided:

Month

month (MMM-DD) of cumulative statistics

Mean

monthly mean of all cumulative flows for a given month of the year

Median

monthly mean of all cumulative flows for a given month of the year

Maximum

monthly mean of all cumulative flows for a given month of the year

Minimum

monthly mean of all cumulative flows for a given month of the year

P'n'

each monthly n-th percentile selected of all cumulative flows for a given month of the year

Default percentile columns:

P5

monthly 5th percentile of all cumulative flows for a given month of the year

P25

monthly 25th percentile of all cumulative flows for a given month of the year

P75

monthly 75th percentile of all cumulative flows for a given month of the year

P95

monthly 95th percentile of all cumulative flows for a given month of the year

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

Examples

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

# Calculate annual monthly cumulative volume statistics
calc_monthly_cumulative_stats(station_number = "08NM116") 

# Calculate annual monthly cumulative volume statistics with default HYDAT basin area
calc_monthly_cumulative_stats(station_number = "08NM116",
                              use_yield = TRUE) 

# Calculate annual monthly cumulative volume statistics with custom basin area
calc_monthly_cumulative_stats(station_number = "08NM116",
                              use_yield = TRUE,
                              basin_area = 800) 
                              
}

Example output



fasstr documentation built on Dec. 11, 2021, 9:55 a.m.