calc_annual_stat_trend {HyMETT}

Calculate trend in annual statistics

Description

Calculate trend in annual statistics

Usage

calc_annual_stat_trend(data = NULL, year, value, ...)

Arguments

data

'data.frame'. Optional data.frame input, with columns containing year and value. Column names are specified as strings in the corresponding parameter. Default is NULL.

year

'numeric' vector when data = NULL, or 'character' string identifying year column name when data is specified. Year of each value in value parameter.

value

'numeric' vector when data = NULL, or 'character' string identifying value column name when data is specified. Values to calculate trend on.

...

further arguments to be passed to or from EnvStats::kendallTrendTest.

Details

This function is a wrapper for EnvStats::kendallTrendTest with the passed equation value ~ year. The returned values include Mann-Kendall test statistic and p-value, Theil-Sen slope and intercept values, and trend details (Millard, 2013; Helsel and others, 2020).

z_stat

Mann-Kendall test statistic, returned directly from EnvStats::kendallTrendTest

p_value

z_stat p-value, returned directly from EnvStats::kendallTrendTest

sen_slope

Sen slope in units value per year, returned directly from EnvStats::kendallTrendTest

intercept

Sen slope intercept, returned directly from EnvStats::kendallTrendTest

trend_mag

Trend magnitude over entire period, in units of value, calculated as ⁠sen_slope * (max(year)⁠ - ⁠min(year))⁠

val_beg/end

Calculated value at beginning or end of period, calculated as sen_slope * year + intercept

val_perc_change

Percentage change over period, calculated as (val_end - val_beg) / val_beg * 100

Value

A tibble (see tibble::tibble) with test statistic, p-value, trend coefficients, and trend calculations. See Details.

References

Millard, S.P., 2013, EnvStats: An R Package for Environmental Statistics: New York, New York, Springer, 291 p. [Also available at https://doi.org/10.1007/978-1-4614-8456-1.]

Helsel, D.R., Hirsch, R.M., Ryberg, K.R., Archfield, S.A., and Gilroy, E.J., 2020, Statistical methods in water resources: U.S. Geological Survey Techniques and Methods, book 4, chap. A3, 458 p. [Also available at https://doi.org/10.3133/tm4a3.]

See Also

kendallTrendTest

Examples

calc_annual_stat_trend(data = example_annual, year = "WY", value = "annual_mean")