dry_spells

Two R functions for finding dry spells in precipitation time series.

Description

This script was written to filter out dry spells in climate time series data and obtain a human-readable summary.

count_consecutive(x) retains a numeric vector with a count of days since the last precipitation was measured.

dryspells_readable(x, dates, threshold = 0) creates a dataframe with start and end date of dryspells, and gives the length in a separate column.

Usage

Before you can use the function, make sure to source("count_consecutive.R") resp. source("dryspells_readable.R") to load the function into your environment. Alternatively, you can also copy the function code into your own script and parse it before using.

## For a simple count since the last precipitation measured
count_consecutive(x)

## For a readable start and end dataframe with length of the period
dryspells_readable(x, dates, threshold = 0)

Arguments

x

A numeric vector, containing the measured precipitation.

dates

A vector of dates, formatted as a date class. Will be used for the output of start and end dates as well as for calculating the length of the period.

threshold

Numeric or integer stating up to which amount of measured precipitation a day is considered to be dry.

Examples

# create random data for testing
measurements <- data.frame(
  precipitation = abs(rnorm(200, 0, 1)),
  date = seq.Date(
    from = as.Date("2017-05-01"),
    by = "day",
    length.out = 200
  )
)

# to obtain some more dry periods in the test data
measurements$precipitation[
  measurements$precipitation < .5
] <- 0

# source functions
source("count_consecutive.R")
source("dryspells_readable.R")

# run functions
dry_daycount <- count_consecutive(measurements$precipitation)
dry_readable <- find_dryspells(
  x = measurements$precipitation,
  dates = measurements$date,
  threshold = .6
)

# view the results
print(dry_daycount)
View(dry_readable)