Description Usage Arguments Details Value References See Also Examples

View source: R/growing_degree_days.R

Calculate the sum of of degree days (average temperature - base
temperature `base_temp`

for each day) during specified dates
for a tibble or data frame of daily weather data. Alternatively, a
number of days before or after a specific date may be
specified. Note that the maximum temperature is capped at
`maxt_cap`

when calculating the average temperature.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 |

`data` |
Tibble or dataframe of daily weather data |

`varmax` |
Name of variable containing max temp (default 'maxt') |

`varmin` |
Name of variable containing min temp (default 'mint') |

`datevar` |
Date variable specifying day (Default: date_met) |

`maxt_cap` |
A numeric value set to the temperature considered to be the maximum necessary for plant growth. Maximum temperature is capped at this value for calculating average daily temp (Default: 30) |

`base_temp` |
A numeric value set to the temperature considered to be the minimum necessary for plant growth (Default: 5) |

`na.rm` |
Used for calculations (Default: FALSE) |

`ndays` |
Number of days after/before the start or end date, respectively. Ignored of both the start and end dates are specified (Default: 5) |

`startdate` |
Start date of data to be extracted |

`enddate` |
Final date of data to be extracted |

`monitor` |
For debugging. Prints data and dates. (Default: FALSE) |

`warn.consecutive` |
A logical indicating whether to check that dates are consecutive, that none are missing and provide a warning if not (Default:TRUE) |

The value returned is the sum of of degree days *GDD = ∑_i
(Tmax_i + Tmin_i) / 2 - Tbase* during specified dates for a tibble
or data frame of daily weather data. The maximum temperature Tmax
is capped at `maxt_cap`

degrees when calculating average temp
(see https://farmwest.com/climate/calculator-information/gdd/ or
McMaster, GS, & Wilhelm, WW (1997)). Baskerville, G &
Emin, P (1969) provide variations on this method.

The sum of degree days is returned but if there are any missing
values, then the value returned will be `NA`

since the
default `na.rm`

is `TRUE`

. Note that if there are any
missing dates, then a warning is issued but the sum of non-missing
values is returned.

If any values are missing, while the sum of degree days may prove useful, it will not include all the data and so will lead to biased underestimates. Hence, in these cases it is unlikely that the value returned is a good estimate but the appropriateness of the estimate will depend on the exact circumstances of the missing data and so this decision is left to the user.

Numeric variable containing the sum of degree days during the period

Baskerville, G., & Emin, P. (1969). Rapid Estimation of Heat Accumulation from Maximum and Minimum Temperatures. Ecology, 50(3), 514-517. doi: 10.2307/1933912

McMaster, G. S., & Wilhelm, W. W. (1997). Growing degree-days: One equation, two interpretations. Agricultural and Forest Meteorology, 87(4), 291–300. doi: 10.1016/S0168-1923(97)00027-0

Anon. (2021). GDD. Farmwest. Retrieved June 15, 2021, from https://farmwest.com/climate/calculator-information/gdd/

`cumulative`

, `daily_mean`

,
`stress_days_over`

, and
`weather_extract`

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | ```
## Selected calculations
library(tidyverse)
growing_degree_days(boonah, enddate = crop$flower_date[4], ndays = 3,
varmax = maxt, varmin = mint,
monitor = TRUE)
growing_degree_days(boonah, enddate = crop$harvest_date[4], ndays = 3,
varmax = maxt, varmin = mint,
monitor = TRUE)
growing_degree_days(boonah, startdate = crop$flower_date[4],
varmax = maxt, varmin = mint,
enddate = crop$harvest_date[4], monitor = TRUE)
## Add selected growing degree days at 'boonah' to 'crop' tibble
## using 'map2_dbl' from the 'purrr' package
## Note: using equivalent 'furrr' functions can speed up calculations
crop2 <- crop %>%
mutate(gddays8_post_sow_7d =
map_dbl(sowing_date, function(x)
growing_degree_days(boonah, startdate = x, ndays = 7,
base_temp = 8)),
gddays_flower_harvest =
map2_dbl(flower_date, harvest_date, function(x, y)
growing_degree_days(boonah, startdate = x, enddate = y)))
crop2
``` |

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