R/compute_hydat_peak_frequencies.R
compute_hydat_peak_frequencies.RdPerforms a volume frequency analysis on annual peak statistics (instantaneous minimums or maximums) extracted from
HYDAT. Calculates statistics from all years, unless specified. The data argument is not available. Analysis
methodology replicates that from HEC-SSP. Returns a list of tibbles
and plots.
compute_hydat_peak_frequencies(
station_number,
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,
1e-04),
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),
start_year,
end_year,
exclude_years,
plot_curve = TRUE
)A character string vector of seven digit Water Survey of Canada station numbers (e.g. "08NM116") of
which to extract annual peak minimum or maximum instantaneous streamflow data from a HYDAT database. Requires tidyhydat
package and a HYDAT database.
Logical value to indicate using maximums rather than the minimums for analysis. Default FALSE.
Logical value to indicate log-scale transforming of flow data before analysis. Default FALSE.
Character string indicating the plotting positions used in the frequency plots, one of 'weibull',
'median', or 'hazen'. Points are plotted against (i-a)/(n+1-a-b) where i is the rank of the value; n is the
sample size and a and b are defined as: (a=0, b=0) for Weibull plotting positions; (a=.2; b=.3) for Median
plotting positions; and (a=.5; b=.5) for Hazen plotting positions. Default 'weibull'.
Numeric vector of probabilities to be plotted along the X axis in the frequency plot. Inverse of
return period. Default c(.9999, .999, .99, .9, .5, .2, .1, .02, .01, .001, .0001).
Character string identifying the distribution to fit annual data, one of 'PIII' (Log Pearson Type III)
or 'weibull' (Weibull) distributions. Default 'PIII'.
Character string identifying the method used to fit the distribution, one of 'MOM' (method of
moments) or 'MLE' (maximum likelihood estimation). Selected as 'MOM' if fit_distr ='PIII' (default) or
'MLE' if fit_distr = 'weibull'.
Numeric vector of quantiles to be estimated from the fitted distribution.
Default c(.975, .99, .98, .95, .90, .80, .50, .20, .10, .05, .01).
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.
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.
Numeric vector of years to exclude from analysis. Leave blank or set to NULL to include all years.
Logical value to indicate plotting the computed curve on the probability plot. Default TRUE.
A list with the following elements:
Data frame with computed annual summary statistics used in analysis.
Data frame with co-ordinates used in frequency plot.
ggplot2 object with frequency plot
List of fitted objects from fitdistrplus.
Data frame with fitted quantiles.
if (FALSE) {
# Working examples (see arguments for further analysis options):
# Compute an annual peak frequency analysis using default arguments (instantaneous lows)
results <- compute_hydat_peak_frequencies(station_number = "08NM116",
start_year = 1980,
end_year = 2010)
# Compute an annual peak frequency analysis using default arguments (instantaneous highs)
results <- compute_hydat_peak_frequencies(station_number = "08NM116",
start_year = 1980,
end_year = 2010,
use_max = TRUE)
}