degreedays: Calculate degree-days

In DesiQuintans/desiderata: Assorted utility functions

Calculate degree-days

Description

"In a nutshell: heating degree days are a measure of how much (in degrees), and for how long (in days), the air temperature was below a certain level." — Martin Bromley, http://www.degreedays.net/introduction

Usage

degreedays(min, max, base, method = "modavg")

Arguments

min	(Numeric) The lowest temperature in the day.
max	(Numeric) The highest temperature in the day.
base	(Numeric) The threshold for counting degree-days. This could be the temperature when plants begin their spring growth or insects become noticeably active, or some other biologically-meaningful baseline.
method	(String, avg or modavg) The calculation method to use (see above). Default is modavg.

Details

This function exposes two calculation methods that were taken from

Herms, Daniel A. 2013. “Using Degree-Days and Plant Phenology to Predict Pest Activity.” IPM of Midwest Landscapes: Tactics and Tools for IPM. 2013. http://cues.cfans.umn.edu/old/IPM-Tactics/IPM-tactics.html.

Average method (avg)

"If the maximum temperature for the day never rises above the base temperature, then no development occurs, and zero degree-days accumulate (we don't calculate negative degree-day values since the development of organisms does not reverse when it is cold)." — Daniel A. Herms

Modified Average (modavg)

"When the daily temperature fluctuates above and below the base temperature (as it does frequently in the spring), the Average Method can underestimate the number of degree-days actually experienced by a plant or insect. In this situation, the Modified Average Method will calculate a higher number of degree-days, and thus can be more accurate for predicting pest activity than the Average Method." — Daniel A. Herms

Value

A numeric vector of the same length as min and max, with each entry containing the degree-day value for that day.

Authors

• Desi Quintans (http://www.desiquintans.com)

• Daniel A. Herms https://scholar.google.com/citations?user=yMYvlKsAAAAJ&hl=en

Source

Herms, Daniel A. 2013. “Using Degree-Days and Plant Phenology to Predict Pest Activity.” IPM of Midwest Landscapes: Tactics and Tools for IPM. 2013. http://cues.cfans.umn.edu/old/IPM-Tactics/IPM-tactics.html.

Examples

degreedays(min = c(19, 20, 20, 21), max = c(25, 24, 23, 22), base = 22, method = "modavg")

#> [1] 1.5 1.0 0.5 0.0

DesiQuintans/desiderata documentation built on April 9, 2023, 5:43 a.m.