Description Usage Arguments Value See Also Examples
View source: R/compute_annual_frequencies.R
Performs a flow volume frequency analysis on annual statistics from a daily streamflow data set. Defaults to a low
flow frequency analysis using annual minimums. Set use_max = TRUE
for annual high flow frequency analyses. Calculates
statistics from all values, unless specified. Function will calculate using all values in 'Values' column (no grouped analysis).
Analysis methodology replicates that from HECSSP. Returns a list of
tibbles and plots.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  compute_annual_frequencies(
data,
dates = Date,
values = Value,
station_number,
roll_days = c(1, 3, 7, 30),
roll_align = "right",
use_max = FALSE,
use_log = FALSE,
prob_plot_position = c("weibull", "median", "hazen"),
prob_scale_points = c(0.9999, 0.999, 0.99, 0.9, 0.5, 0.2, 0.1, 0.02, 0.01, 0.001,
0.0001),
fit_distr = c("PIII", "weibull"),
fit_distr_method = ifelse(fit_distr == "PIII", "MOM", "MLE"),
fit_quantiles = c(0.975, 0.99, 0.98, 0.95, 0.9, 0.8, 0.5, 0.2, 0.1, 0.05, 0.01),
plot_curve = TRUE,
water_year_start = 1,
start_year,
end_year,
exclude_years,
months = 1:12,
ignore_missing = FALSE,
allowed_missing = ifelse(ignore_missing, 100, 0)
)

data 
A data frame of daily data that contains columns of dates and flow values. Groupings and the 
dates 
Name of column in 
values 
Name of column in 
station_number 
Character string vector of seven digit Water Survey of Canada station numbers (e.g. 
roll_days 
Numeric value of the number of days to apply a rolling mean. Default 
roll_align 
Character string identifying the direction of the rolling mean from the specified date, either by the first
( 
use_max 
Logical value to indicate using maximums rather than the minimums for analysis. Default 
use_log 
Logical value to indicate logscale transforming of flow data before analysis. Default 
prob_plot_position 
Character string indicating the plotting positions used in the frequency plots, one of 
prob_scale_points 
Numeric vector of probabilities to be plotted along the X axis in the frequency plot. Inverse of
return period. Default 
fit_distr 
Character string identifying the distribution to fit annual data, one of 
fit_distr_method 
Character string identifying the method used to fit the distribution, one of 
fit_quantiles 
Numeric vector of quantiles to be estimated from the fitted distribution.
Default 
plot_curve 
Logical value to indicate plotting the computed curve on the probability plot. Default 
water_year_start 
Numeric value indicating the month ( 
start_year 
Numeric value of the first year to consider for analysis. Leave blank or set well before start date (i.e.

end_year 
Numeric value of the last year to consider for analysis. Leave blank or set well after end date (i.e.

exclude_years 
Numeric vector of years to exclude from analysis. Leave blank or set to 
months 
Numeric vector of months to include in analysis. For example, 
ignore_missing 
Logical value indicating whether dates with missing values should be included in the calculation. If

allowed_missing 
Numeric value between 0 and 100 indicating the percentage of missing dates allowed to be
included to calculate a statistic (0 to 100 percent). If 
A list with the following elements:
Freq_Analysis_Data 
Data frame with computed annual summary statistics used in analysis. 
Freq_Plot_Data 
Data frame with coordinates used in frequency plot. 
Freq_Plot 
ggplot2 object with frequency plot. 
Freq_Fitting 
List of fitted objects from fitdistrplus. 
Freq_Fitted_Quantiles 
Data frame with fitted quantiles. 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  ## Not run:
# Working examples (see arguments for further analysis options):
# Compute an annual frequency analysis using default arguments
results < compute_annual_frequencies(station_number = "08NM116",
start_year = 1980,
end_year = 2010)
# Compute an annual frequency analysis using default arguments (as listed)
results < compute_annual_frequencies(station_number = "08NM116",
roll_days = c(1,3,7,30),
start_year = 1980,
end_year = 2010,
prob_plot_position = "weibull",
prob_scale_points = c(.9999, .999, .99, .9, .5,
.2, .1, .02, .01, .001, .0001),
fit_distr = "PIII",
fit_distr_method = "MOM")
# Compute a 7day annual frequency analysis with "median" plotting positions
# and fitting the data to a weibull distribution (not default PIII)
results < compute_annual_frequencies(station_number = "08NM116",
roll_days = 7,
start_year = 1980,
end_year = 2010,
prob_plot_position = "median",
fit_distr = "weibull")
## End(Not run)

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