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Detect and summarize drought events from SPEI droughts index time series

Source: R/droughts.R
droughts.Rd

Identifies drought events in a time series when a given index (e.g., SPEI) falls below a specified threshold for at least two consecutive months. Returns the processed dataset, the detected drought events, and a summary of their characteristics.

Usage

droughts(df, vname, threshold, min_duration = 2)

Arguments

df

A data.frame or tibble containing the time series data. Must include either:

  • a date column of class Date or POSIXct, or

  • separate year and month columns.

  • a numeric column specified by vname that contains the drought index values.

vname

A string indicating the name of the numeric column to be evaluated (e.g., "spei12").

threshold

A numeric threshold below which values are considered part of a drought event.

min_duration

Minimum number of consecutive months below threshold required for an event to be considered a drought. Default is 2.

Value

A named list with three elements:

  • data: the original data frame with drought flags and durations.

  • drought_events: only the rows that are part of drought events (duration >= min_duration).

  • drought_assessment: summary of each event, including duration, intensity, severity, and timing.

Examples

data(spei_granada)
# Detect droughts in the SPEI-12 time series with a threshold of -1.28
droughts_result <- droughts(spei_granada, vname = "spei12", threshold = -1.28)