View source: R/calc_monthly_stats.R
calc_monthly_stats  R Documentation 
Calculates means, medians, maximums, minimums, and percentiles for each month of all years of flow values from a daily streamflow data set. Calculates statistics from all values, unless specified. Returns a tibble with statistics.
calc_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,
transpose = FALSE,
spread = FALSE,
complete_years = FALSE,
ignore_missing = FALSE,
allowed_missing = ifelse(ignore_missing, 100, 0)
)
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 
dates 
Name of column in 
values 
Name of column in 
groups 
Name of column in 
station_number 
Character string vector of seven digit Water Survey of Canada station numbers (e.g. 
percentiles 
Numeric vector of percentiles to calculate. Set to 
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
( 
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, 
transpose 
Logical value indicating if each month statistic should be individual rows. Default 
spread 
Logical value indicating if each month statistic should be the column name. Default 
complete_years 
Logical values indicating whether to include only years with complete data in analysis. Default 
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 tibble data frame with the following columns:
Year 
calendar or water year selected 
Month 
month of the year 
Mean 
mean of all daily flows for a given month and year 
Median 
median of all daily flows for a given month and year 
Maximum 
maximum of all daily flows for a given month and year 
Minimum 
minimum of all daily flows for a given month and year 
P'n' 
each nth percentile selected for a given month and year 
Default percentile columns:
P10 
10th percentile of all daily flows for a given month and year 
P90 
90th percentile of all daily flows for a given month and year 
Transposing data creates a column of 'Statistics' for each month, labeled as 'MonthStatistic' (ex "JanMean"), and subsequent columns for each year selected. Spreading data creates columns of Year and subsequent columns of MonthStatistics (ex 'JanMean').
# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {
# Calculate statistics using a data frame and data argument with defaults
flow_data < tidyhydat::hy_daily_flows(station_number = "08NM116")
calc_monthly_stats(data = flow_data,
start_year = 1980)
# Calculate statistics using station_number argument with defaults
calc_monthly_stats(station_number = "08NM116",
start_year = 1980)
# Calculate statistics regardless if there is missing data for a given year
calc_monthly_stats(station_number = "08NM116",
ignore_missing = TRUE)
# Calculate statistics for water years starting in October
calc_monthly_stats(station_number = "08NM116",
start_year = 1980,
water_year_start = 10)
# Calculate statistics with custom years and percentiles
calc_monthly_stats(station_number = "08NM116",
start_year = 1981,
end_year = 2010,
exclude_years = c(1991,1993:1995),
percentiles = c(25,75))
}
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