fasstr (version 0.3.1)

calc_longterm_monthly_stats: Calculate long-term summary statistics from annual monthly mean flows

Description

Calculates the long-term and long-term monthly mean, median, maximum, minimum, and percentiles of monthly mean flow values from a streamflow dataset. Calculates the statistics from all annual monthly mean values from all years, unless specified.

Usage

calc_longterm_monthly_stats(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  percentiles = c(10, 90),
  roll_days = 1,
  roll_align = "right",
  water_year_start = 1,
  start_year,
  end_year,
  exclude_years,
  months = 1:12,
  complete_years = FALSE,
  include_annual = TRUE,
  custom_months,
  custom_months_label,
  transpose = FALSE,
  ignore_missing = FALSE
)

Arguments

data

A 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

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

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

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

A 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(10,90).

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 of the start of the 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).

complete_years

Logical values indicating whether to include only years with complete data in analysis. Default FALSE.

include_annual

Logical value indicating whether to include annual calculation of all months. Default TRUE.

custom_months

Numeric vector of months to combine to summarize (ex. 6:8 for Jun-Aug). Adds results to the end of table. If wanting months that overlap calendar years (ex. Oct-Mar), choose water_year_start that begins before the first month listed. Leave blank for no custom month summary.

custom_months_label

Character string to label custom months. For example, if choosing months 7:9 you may choose "Summer" or "Jul-Sep". Default "Custom-Months".

transpose

Logical value indicating if the results rows and columns are to be switched. Default FALSE.

ignore_missing

Logical value indicating whether dates with missing values should be included in the calculation. If TRUE then a statistic will be calculated regardless of missing dates. If FALSE then only statistics from time periods with no missing dates will be returned. Default FALSE.

Value

A tibble data frame with the following columns:

Month

month of the year, included 'Annual' for all months, and 'Custom-Months' if selected

Mean

mean of all annual monthly means for a given month over all years

Median

median of all annual monthly means for a given month over all years

Maximum

maximum of all annual monthly means for a given month over all years

Minimum

minimum of all annual monthly means for a given month over all years

P'n'

each n-th percentile selected for annual monthly means for a given month over all years

Default percentile columns:

P10

annual 10th percentile selected for annual monthly means for a given month over all years

P90

annual 90th percentile selected for annual monthly means for a given month over all years

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

Examples

# NOT RUN {
# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {

# Calculate long-term monthly statistics using data argument with defaults
flow_data <- tidyhydat::hy_daily_flows(station_number = "08NM116")
calc_longterm_monthly_stats(data = flow_data,
                            start_year = 1980)

# Calculate long-term monthly statistics using station_number argument with defaults
calc_longterm_monthly_stats(station_number = "08NM116",
                            start_year = 1980)

# Calculate long-term monthly statistics regardless if there is missing data for a given year
calc_longterm_monthly_stats(station_number = "08NM116",
                            ignore_missing = TRUE)
                  
# Calculate long-term monthly statistics for water years starting in October
calc_longterm_monthly_stats(station_number = "08NM116",
                            start_year = 1980,
                            water_year_start = 10)
                  
# Calculate long-term monthly statistics with custom years
calc_longterm_monthly_stats(station_number = "08NM116",
                            start_year = 1981,
                            end_year = 2010,
                            exclude_years = c(1991,1993:1995))
                  
# Calculate long-term monthly statistics for 7-day flows for July-September months only, 
# with 25 and 75th percentiles
calc_longterm_monthly_stats(station_number = "08NM116",
                            roll_days = 7,
                            months = 7:9,
                            percentiles = c(25,75),
                            ignore_missing = TRUE,
                            include_annual = FALSE) # removes the Long-term numbers 
                    
# Calculate long-term monthly statistics and add custom stats for July-September
calc_longterm_monthly_stats(station_number = "08NM116",
                            start_year = 1980,
                            custom_months = 7:9,
                            custom_months_label = "Summer")                  
                            
}
# }