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Factorial designs help us understand synergies and antagonisms between ecological factors. However, meta-analyses of factorial experiments are rare in ecology, likely because extracting effect sizes from factorial data is not straightforward.
minter is an R package that simplifies this process by
providing functions to extract different effect sizes from factorial
data, enabling researchers to conduct meta-analyses of interactions
between factors.
devtools::install_github("fdecunta/minter")library(minter)
# Dummy data from 8 studies examining fertilization × drought on plant biomass
studies <- data.frame(
study_id = 1:8,
# Control: No fertilization, well-watered
Ctrl_mean = c(12.3, 15.7, 10.8, 14.2, 11.9, 13.5, 16.1, 12.7),
Ctrl_sd = c(2.1, 3.2, 1.8, 2.7, 2.3, 2.9, 3.5, 2.4),
Ctrl_n = c(20, 24, 18, 22, 19, 25, 23, 21),
# Fertilization only
Fert_mean = c(18.5, 21.3, 16.2, 19.8, 17.1, 20.4, 22.7, 18.9),
Fert_sd = c(3.1, 4.1, 2.7, 3.6, 3.2, 3.8, 4.2, 3.4),
Fert_n = c(22, 25, 20, 24, 21, 26, 25, 23),
# Drought only
Drought_mean = c(8.7, 11.2, 7.9, 10.1, 8.3, 9.8, 11.7, 9.4),
Drought_sd = c(1.8, 2.4, 1.6, 2.1, 1.9, 2.3, 2.6, 2.0),
Drought_n = c(19, 23, 17, 21, 18, 24, 22, 20),
# Both treatments
Both_mean = c(14.2, 17.8, 12.9, 16.3, 13.7, 16.1, 18.4, 15.2),
Both_sd = c(2.9, 3.7, 2.5, 3.3, 2.8, 3.4, 3.9, 3.1),
Both_n = c(21, 26, 19, 23, 20, 27, 24, 22)
)
# Calculate interaction effect: Does fertilization work differently under drought?
interaction_results <- lnRR_inter(
data = studies,
Ctrl_mean = "Ctrl_mean", Ctrl_sd = "Ctrl_sd", Ctrl_n = "Ctrl_n",
A_mean = "Fert_mean", A_sd = "Fert_sd", A_n = "Fert_n",
B_mean = "Drought_mean", B_sd = "Drought_sd", B_n = "Drought_n",
AB_mean = "Both_mean", AB_sd = "Both_sd", AB_n = "Both_n"
)
head(interaction_results)
#> study_id Ctrl_mean Ctrl_sd ... yi vi
#> 1 1 12.3 2.1 0.081 0.0069
#> 2 2 15.7 3.2 0.158 0.0068
#> 3 3 10.8 1.8 0.084 0.0073
# Meta-analysis
library(metafor)
res <- rma(yi, vi, ..., data = interaction_results)We thank Shinichi Nakagawa and Daniel Noble for generously sharing their unpublished formulas for meta-analysis of interactions, which form the theoretical foundation of this package.
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They may not be fully stable and should be used with caution. We make no claims about them.
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